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✏️ Editing: 3.5.html

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 <div class="section" id="what-s-new-in-python-3-5">
<h1>What’s New In Python 3.5<a class="headerlink" href="#what-s-new-in-python-3-5" title="Permalink to this headline">¶</a></h1>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Editors:</th><td class="field-body">Elvis Pranskevichus &lt;<a class="reference external" href="mailto:elvis&#37;&#52;&#48;magic&#46;io">elvis&#64;magic&#46;io</a>&gt;, Yury Selivanov &lt;<a class="reference external" href="mailto:yury&#37;&#52;&#48;magic&#46;io">yury&#64;magic&#46;io</a>&gt;</td>
</tr>
</tbody>
</table>
This article explains the new features in Python 3.5, compared to 3.4.
Python 3.5 was released on September 13, 2015. &nbsp;See the
<a class="reference external" href="https://docs.python.org/3.5/whatsnew/changelog.html">changelog</a> for a full
list of changes.
<div class="admonition seealso">
See also
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0478">PEP 478</a> - Python 3.5 Release Schedule
</div>
<div class="section" id="summary-release-highlights">
<h2>Summary – Release highlights<a class="headerlink" href="#summary-release-highlights" title="Permalink to this headline">¶</a></h2>
New syntax features:
<ul class="simple">
<li><a class="reference internal" href="#whatsnew-pep-492">PEP 492</a>, coroutines with async and await syntax.</li>
<li><a class="reference internal" href="#whatsnew-pep-465">PEP 465</a>, a new matrix multiplication operator: <code class="docutils literal notranslate">a &#64; b</code>.</li>
<li><a class="reference internal" href="#whatsnew-pep-448">PEP 448</a>, additional unpacking generalizations.</li>
</ul>
New library modules:
<ul class="simple">
<li><a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see PEP 484)."><code class="xref py py-mod docutils literal notranslate">typing</code></a>: <a class="reference internal" href="#whatsnew-pep-484">PEP 484 – Type Hints</a>.</li>
<li><a class="reference internal" href="../library/zipapp.html#module-zipapp" title="zipapp: Manage executable python zip archives"><code class="xref py py-mod docutils literal notranslate">zipapp</code></a>: <a class="reference internal" href="#whatsnew-zipapp">PEP 441 Improving Python ZIP Application Support</a>.</li>
</ul>
New built-in features:
<ul class="simple">
<li><code class="docutils literal notranslate">bytes % args</code>, <code class="docutils literal notranslate">bytearray % args</code>: <a class="reference internal" href="#whatsnew-pep-461">PEP 461</a> –
Adding <code class="docutils literal notranslate">%</code> formatting to bytes and bytearray.</li>
<li>New <a class="reference internal" href="../library/stdtypes.html#bytes.hex" title="bytes.hex"><code class="xref py py-meth docutils literal notranslate">bytes.hex()</code></a>, <a class="reference internal" href="../library/stdtypes.html#bytearray.hex" title="bytearray.hex"><code class="xref py py-meth docutils literal notranslate">bytearray.hex()</code></a> and <a class="reference internal" href="../library/stdtypes.html#memoryview.hex" title="memoryview.hex"><code class="xref py py-meth docutils literal notranslate">memoryview.hex()</code></a>
methods. (Contributed by Arnon Yaari in <a class="reference external" href="https://bugs.python.org/issue9951">bpo-9951</a>.)</li>
<li><a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate">memoryview</code></a> now supports tuple indexing (including multi-dimensional).
(Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue23632">bpo-23632</a>.)</li>
<li>Generators have a new <code class="docutils literal notranslate">gi_yieldfrom</code> attribute, which returns the
object being iterated by <code class="docutils literal notranslate">yield from</code> expressions. (Contributed
by Benno Leslie and Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue24450">bpo-24450</a>.)</li>
<li>A new <a class="reference internal" href="../library/exceptions.html#RecursionError" title="RecursionError"><code class="xref py py-exc docutils literal notranslate">RecursionError</code></a> exception is now raised when maximum
recursion depth is reached. (Contributed by Georg Brandl
in <a class="reference external" href="https://bugs.python.org/issue19235">bpo-19235</a>.)</li>
</ul>
CPython implementation improvements:
<ul class="simple">
<li>When the <code class="docutils literal notranslate">LC_TYPE</code> locale is the POSIX locale (<code class="docutils literal notranslate">C</code> locale),
<a class="reference internal" href="../library/sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-data docutils literal notranslate">sys.stdin</code></a> and <a class="reference internal" href="../library/sys.html#sys.stdout" title="sys.stdout"><code class="xref py py-data docutils literal notranslate">sys.stdout</code></a> now use the
<code class="docutils literal notranslate">surrogateescape</code> error handler, instead of the <code class="docutils literal notranslate">strict</code> error handler.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue19977">bpo-19977</a>.)</li>
<li><code class="docutils literal notranslate">.pyo</code> files are no longer used and have been replaced by a more flexible
scheme that includes the optimization level explicitly in <code class="docutils literal notranslate">.pyc</code> name.
(See <a class="reference internal" href="#whatsnew-pep-488">PEP 488 overview</a>.)</li>
<li>Builtin and extension modules are now initialized in a multi-phase process,
which is similar to how Python modules are loaded.
(See <a class="reference internal" href="#whatsnew-pep-489">PEP 489 overview</a>.)</li>
</ul>
Significant improvements in the standard library:
<ul class="simple">
<li><a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate">collections.OrderedDict</code></a> is now
<a class="reference internal" href="#whatsnew-ordereddict">implemented in C</a>, which makes it
4 to 100 times faster.</li>
<li>The <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate">ssl</code></a> module gained
<a class="reference internal" href="#whatsnew-sslmemorybio">support for Memory BIO</a>, which decouples SSL
protocol handling from network IO.</li>
<li>The new <a class="reference internal" href="../library/os.html#os.scandir" title="os.scandir"><code class="xref py py-func docutils literal notranslate">os.scandir()</code></a> function provides a
<a class="reference internal" href="#whatsnew-pep-471">better and significantly faster way</a>
of directory traversal.</li>
<li><a class="reference internal" href="../library/functools.html#functools.lru_cache" title="functools.lru_cache"><code class="xref py py-func docutils literal notranslate">functools.lru_cache()</code></a> has been mostly
<a class="reference internal" href="#whatsnew-lrucache">reimplemented in C</a>, yielding much better
performance.</li>
<li>The new <a class="reference internal" href="../library/subprocess.html#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate">subprocess.run()</code></a> function provides a
<a class="reference internal" href="#whatsnew-subprocess">streamlined way to run subprocesses</a>.</li>
<li>The <a class="reference internal" href="../library/traceback.html#module-traceback" title="traceback: Print or retrieve a stack traceback."><code class="xref py py-mod docutils literal notranslate">traceback</code></a> module has been significantly
<a class="reference internal" href="#whatsnew-traceback">enhanced</a> for improved
performance and developer convenience.</li>
</ul>
Security improvements:
<ul class="simple">
<li>SSLv3 is now disabled throughout the standard library.
It can still be enabled by instantiating a <a class="reference internal" href="../library/ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate">ssl.SSLContext</code></a>
manually. (See <a class="reference external" href="https://bugs.python.org/issue22638">bpo-22638</a> for more details; this change was
backported to CPython 3.4 and 2.7.)</li>
<li>HTTP cookie parsing is now stricter, in order to protect
against potential injection attacks. (Contributed by Antoine Pitrou
in <a class="reference external" href="https://bugs.python.org/issue22796">bpo-22796</a>.)</li>
</ul>
Windows improvements:
<ul class="simple">
<li>A new installer for Windows has replaced the old MSI.
See <a class="reference internal" href="../using/windows.html#using-on-windows">Using Python on Windows</a> for more information.</li>
<li>Windows builds now use Microsoft Visual C++ 14.0, and extension modules
should use the same.</li>
</ul>
Please read on for a comprehensive list of user-facing changes, including many
other smaller improvements, CPython optimizations, deprecations, and potential
porting issues.
</div>
<div class="section" id="new-features">
<h2>New Features<a class="headerlink" href="#new-features" title="Permalink to this headline">¶</a></h2>
<div class="section" id="pep-492-coroutines-with-async-and-await-syntax">
<h3>PEP 492 - Coroutines with async and await syntax<a class="headerlink" href="#pep-492-coroutines-with-async-and-await-syntax" title="Permalink to this headline">¶</a></h3>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0492">PEP 492</a> greatly improves support for asynchronous programming in Python
by adding <a class="reference internal" href="../glossary.html#term-awaitable">awaitable objects</a>,
<a class="reference internal" href="../glossary.html#term-coroutine-function">coroutine functions</a>,
<a class="reference internal" href="../glossary.html#term-asynchronous-iterable">asynchronous iteration</a>,
and <a class="reference internal" href="../glossary.html#term-asynchronous-context-manager">asynchronous context managers</a>.
Coroutine functions are declared using the new <a class="reference internal" href="../reference/compound_stmts.html#async-def"><code class="xref std std-keyword docutils literal notranslate">async def</code></a> syntax:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; async def coro():
... return &#39;spam&#39;
</pre></div>
</div>
Inside a coroutine function, the new <a class="reference internal" href="../reference/expressions.html#await"><code class="xref std std-keyword docutils literal notranslate">await</code></a> expression can be used
to suspend coroutine execution until the result is available. Any object
can be awaited, as long as it implements the <a class="reference internal" href="../glossary.html#term-awaitable">awaitable</a> protocol by
defining the <a class="reference internal" href="../reference/datamodel.html#object.__await__" title="object.__await__"><code class="xref py py-meth docutils literal notranslate">__await__()</code></a> method.
PEP 492 also adds <a class="reference internal" href="../reference/compound_stmts.html#async-for"><code class="xref std std-keyword docutils literal notranslate">async for</code></a> statement for convenient iteration
over asynchronous iterables.
An example of a rudimentary HTTP client written using the new syntax:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>import asyncio

async def http_get(domain):
 reader, writer = await asyncio.open_connection(domain, 80)

writer.write(b&#39;\r\n&#39;.join([
 b&#39;GET / HTTP/1.1&#39;,
 b&#39;Host: %b&#39; % domain.encode(&#39;latin-1&#39;),
 b&#39;Connection: close&#39;,
 b&#39;&#39;, b&#39;&#39;
 ]))

async for line in reader:
 print(&#39;&gt;&gt;&gt;&#39;, line)

writer.close()

async def coro(name, lock):
 print(&#39;coro {}: waiting for lock&#39;.format(name))
 async with lock:
 print(&#39;coro {}: holding the lock&#39;.format(name))
 await asyncio.sleep(1)
 print(&#39;coro {}: releasing the lock&#39;.format(name))

loop = asyncio.get_event_loop()
lock = asyncio.Lock()
coros = asyncio.gather(coro(1, lock), coro(2, lock))
try:
 loop.run_until_complete(coros)
finally:
 loop.close()
</pre></div>
</div>
will output:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>coro 2: waiting for lock
coro 2: holding the lock
coro 1: waiting for lock
coro 2: releasing the lock
coro 1: holding the lock
coro 1: releasing the lock
</pre></div>
</div>
Note that both <a class="reference internal" href="../reference/compound_stmts.html#async-for"><code class="xref std std-keyword docutils literal notranslate">async for</code></a> and <a class="reference internal" href="../reference/compound_stmts.html#async-with"><code class="xref std std-keyword docutils literal notranslate">async with</code></a> can only
be used inside a coroutine function declared with <a class="reference internal" href="../reference/compound_stmts.html#async-def"><code class="xref std std-keyword docutils literal notranslate">async def</code></a>.
Coroutine functions are intended to be run inside a compatible event loop,
such as the <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio-event-loop">asyncio loop</a>.
<div class="admonition note">
Note
<div class="last versionchanged">
Changed in version 3.5.2: Starting with CPython 3.5.2, <code class="docutils literal notranslate">__aiter__</code> can directly return
<a class="reference internal" href="../glossary.html#term-asynchronous-iterator">asynchronous iterators</a>. Returning
an <a class="reference internal" href="../glossary.html#term-awaitable">awaitable</a> object will result in a
<a class="reference internal" href="../library/exceptions.html#PendingDeprecationWarning" title="PendingDeprecationWarning"><code class="xref py py-exc docutils literal notranslate">PendingDeprecationWarning</code></a>.
See more details in the <a class="reference internal" href="../reference/datamodel.html#async-iterators">Asynchronous Iterators</a> documentation
section.
</div>
</div>
<div class="admonition seealso">
See also
<dl class="last docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0492">PEP 492</a> – Coroutines with async and await syntax</dt>
<dd>PEP written and implemented by Yury Selivanov.</dd>
</dl>
</div>
</div>
<div class="section" id="pep-465-a-dedicated-infix-operator-for-matrix-multiplication">
<h3>PEP 465 - A dedicated infix operator for matrix multiplication<a class="headerlink" href="#pep-465-a-dedicated-infix-operator-for-matrix-multiplication" title="Permalink to this headline">¶</a></h3>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0465">PEP 465</a> adds the <code class="docutils literal notranslate">&#64;</code> infix operator for matrix multiplication.
Currently, no builtin Python types implement the new operator, however, it
can be implemented by defining <a class="reference internal" href="../reference/datamodel.html#object.__matmul__" title="object.__matmul__"><code class="xref py py-meth docutils literal notranslate">__matmul__()</code></a>, <a class="reference internal" href="../reference/datamodel.html#object.__rmatmul__" title="object.__rmatmul__"><code class="xref py py-meth docutils literal notranslate">__rmatmul__()</code></a>,
and <a class="reference internal" href="../reference/datamodel.html#object.__imatmul__" title="object.__imatmul__"><code class="xref py py-meth docutils literal notranslate">__imatmul__()</code></a> for regular, reflected, and in-place matrix
multiplication. The semantics of these methods is similar to that of
methods defining other infix arithmetic operators.
Matrix multiplication is a notably common operation in many fields of
mathematics, science, engineering, and the addition of <code class="docutils literal notranslate">&#64;</code> allows writing
cleaner code:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>S = (H @ beta - r).T @ inv(H @ V @ H.T) @ (H @ beta - r)
</pre></div>
</div>
instead of:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>S = dot((dot(H, beta) - r).T,
 dot(inv(dot(dot(H, V), H.T)), dot(H, beta) - r))
</pre></div>
</div>
NumPy 1.10 has support for the new operator:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import numpy

&gt;&gt;&gt; x = numpy.ones(3)
&gt;&gt;&gt; x
array([ 1., 1., 1.])

&gt;&gt;&gt; m = numpy.eye(3)
&gt;&gt;&gt; m
array([[ 1., 0., 0.],
 [ 0., 1., 0.],
 [ 0., 0., 1.]])

&gt;&gt;&gt; x @ m
array([ 1., 1., 1.])
</pre></div>
</div>
<div class="admonition seealso">
See also
<dl class="last docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0465">PEP 465</a> – A dedicated infix operator for matrix multiplication</dt>
<dd>PEP written by Nathaniel J. Smith; implemented by Benjamin Peterson.</dd>
</dl>
</div>
</div>
<div class="section" id="pep-448-additional-unpacking-generalizations">
<h3>PEP 448 - Additional Unpacking Generalizations<a class="headerlink" href="#pep-448-additional-unpacking-generalizations" title="Permalink to this headline">¶</a></h3>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0448">PEP 448</a> extends the allowed uses of the <code class="docutils literal notranslate">*</code> iterable unpacking
operator and <code class="docutils literal notranslate">**</code> dictionary unpacking operator. It is now possible
to use an arbitrary number of unpackings in <a class="reference internal" href="../reference/expressions.html#calls">function calls</a>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; print(*[1], *[2], 3, *[4, 5])
1 2 3 4 5

&gt;&gt;&gt; def fn(a, b, c, d):
... print(a, b, c, d)
...

&gt;&gt;&gt; fn(**{&#39;a&#39;: 1, &#39;c&#39;: 3}, **{&#39;b&#39;: 2, &#39;d&#39;: 4})
1 2 3 4
</pre></div>
</div>
Similarly, tuple, list, set, and dictionary displays allow multiple
unpackings (see <a class="reference internal" href="../reference/expressions.html#exprlists">Expression lists</a> and <a class="reference internal" href="../reference/expressions.html#dict">Dictionary displays</a>):
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; *range(4), 4
(0, 1, 2, 3, 4)

&gt;&gt;&gt; [*range(4), 4]
[0, 1, 2, 3, 4]

&gt;&gt;&gt; {*range(4), 4, *(5, 6, 7)}
{0, 1, 2, 3, 4, 5, 6, 7}

&gt;&gt;&gt; {&#39;x&#39;: 1, **{&#39;y&#39;: 2}}
{&#39;x&#39;: 1, &#39;y&#39;: 2}
</pre></div>
</div>
<div class="admonition seealso">
See also
<dl class="last docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0448">PEP 448</a> – Additional Unpacking Generalizations</dt>
<dd>PEP written by Joshua Landau; implemented by Neil Girdhar,
Thomas Wouters, and Joshua Landau.</dd>
</dl>
</div>
</div>
<div class="section" id="pep-461-percent-formatting-support-for-bytes-and-bytearray">
<h3>PEP 461 - percent formatting support for bytes and bytearray<a class="headerlink" href="#pep-461-percent-formatting-support-for-bytes-and-bytearray" title="Permalink to this headline">¶</a></h3>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0461">PEP 461</a> adds support for the <code class="docutils literal notranslate">%</code>
<a class="reference internal" href="../library/stdtypes.html#bytes-formatting">interpolation operator</a> to <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a>
and <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a>.
While interpolation is usually thought of as a string operation, there are
cases where interpolation on <code class="docutils literal notranslate">bytes</code> or <code class="docutils literal notranslate">bytearrays</code> makes sense, and the
work needed to make up for this missing functionality detracts from the
overall readability of the code. This issue is particularly important when
dealing with wire format protocols, which are often a mixture of binary
and ASCII compatible text.
Examples:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; b&#39;Hello %b!&#39; % b&#39;World&#39;
b&#39;Hello World!&#39;

&gt;&gt;&gt; b&#39;x=%i y=%f&#39; % (1, 2.5)
b&#39;x=1 y=2.500000&#39;
</pre></div>
</div>
Unicode is not allowed for <code class="docutils literal notranslate">%b</code>, but it is accepted by <code class="docutils literal notranslate">%a</code> (equivalent of
<code class="docutils literal notranslate">repr(obj).encode('ascii', 'backslashreplace')</code>):
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; b&#39;Hello %b!&#39; % &#39;World&#39;
Traceback (most recent call last):
 File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
TypeError: %b requires bytes, or an object that implements __bytes__, not &#39;str&#39;

&gt;&gt;&gt; b&#39;price: %a&#39; % &#39;10€&#39;
b&quot;price: &#39;10\\u20ac&#39;&quot;
</pre></div>
</div>
Note that <code class="docutils literal notranslate">%s</code> and <code class="docutils literal notranslate">%r</code> conversion types, although supported, should
only be used in codebases that need compatibility with Python 2.
<div class="admonition seealso">
See also
<dl class="last docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0461">PEP 461</a> – Adding % formatting to bytes and bytearray</dt>
<dd>PEP written by Ethan Furman; implemented by Neil Schemenauer and
Ethan Furman.</dd>
</dl>
</div>
</div>
<div class="section" id="pep-484-type-hints">
<h3>PEP 484 - Type Hints<a class="headerlink" href="#pep-484-type-hints" title="Permalink to this headline">¶</a></h3>
Function annotation syntax has been a Python feature since version 3.0
(<a class="pep reference external" href="https://www.python.org/dev/peps/pep-3107">PEP 3107</a>), however the semantics of annotations has been left undefined.
Experience has shown that the majority of function annotation
uses were to provide type hints to function parameters and return values. It
became evident that it would be beneficial for Python users, if the
standard library included the base definitions and tools for type annotations.
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a> introduces a <a class="reference internal" href="../glossary.html#term-provisional-api">provisional module</a> to
provide these standard definitions and tools, along with some conventions
for situations where annotations are not available.
For example, here is a simple function whose argument and return type
are declared in the annotations:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def greeting(name: str) -&gt; str:
 return &#39;Hello &#39; + name
</pre></div>
</div>
While these annotations are available at runtime through the usual
<code class="xref py py-attr docutils literal notranslate">__annotations__</code> attribute, no automatic type checking happens at
runtime. Instead, it is assumed that a separate off-line type checker
(e.g. <a class="reference external" href="http://mypy-lang.org">mypy</a>) will be used for on-demand
source code analysis.
The type system supports unions, generic types, and a special type
named <a class="reference internal" href="../library/typing.html#typing.Any" title="typing.Any"><code class="xref py py-class docutils literal notranslate">Any</code></a> which is consistent with (i.e. assignable to
and from) all types.
<div class="admonition seealso">
See also
<ul class="last simple">
<li><a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see PEP 484)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> module documentation</li>
<li><dl class="first docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a> – Type Hints</dt>
<dd>PEP written by Guido van Rossum, Jukka Lehtosalo, and Łukasz Langa;
implemented by Guido van Rossum.</dd>
</dl>
</li>
<li><dl class="first docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0483">PEP 483</a> – The Theory of Type Hints</dt>
<dd>PEP written by Guido van Rossum</dd>
</dl>
</li>
</ul>
</div>
</div>
<div class="section" id="pep-471-os-scandir-function-a-better-and-faster-directory-iterator">
<h3>PEP 471 - os.scandir() function – a better and faster directory iterator<a class="headerlink" href="#pep-471-os-scandir-function-a-better-and-faster-directory-iterator" title="Permalink to this headline">¶</a></h3>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0471">PEP 471</a> adds a new directory iteration function, <a class="reference internal" href="../library/os.html#os.scandir" title="os.scandir"><code class="xref py py-func docutils literal notranslate">os.scandir()</code></a>,
to the standard library. Additionally, <a class="reference internal" href="../library/os.html#os.walk" title="os.walk"><code class="xref py py-func docutils literal notranslate">os.walk()</code></a> is now
implemented using <code class="docutils literal notranslate">scandir</code>, which makes it 3 to 5 times faster
on POSIX systems and 7 to 20 times faster on Windows systems. This is
largely achieved by greatly reducing the number of calls to <a class="reference internal" href="../library/os.html#os.stat" title="os.stat"><code class="xref py py-func docutils literal notranslate">os.stat()</code></a>
required to walk a directory tree.
Additionally, <code class="docutils literal notranslate">scandir</code> returns an iterator, as opposed to returning
a list of file names, which improves memory efficiency when iterating
over very large directories.
The following example shows a simple use of <a class="reference internal" href="../library/os.html#os.scandir" title="os.scandir"><code class="xref py py-func docutils literal notranslate">os.scandir()</code></a> to display all
the files (excluding directories) in the given path that don’t start with
<code class="docutils literal notranslate">'.'</code>. The <a class="reference internal" href="../library/os.html#os.DirEntry.is_file" title="os.DirEntry.is_file"><code class="xref py py-meth docutils literal notranslate">entry.is_file()</code></a> call will generally
not make an additional system call:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>for entry in os.scandir(path):
 if not entry.name.startswith(&#39;.&#39;) and entry.is_file():
 print(entry.name)
</pre></div>
</div>
<div class="admonition seealso">
See also
<dl class="last docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0471">PEP 471</a> – os.scandir() function – a better and faster directory iterator</dt>
<dd>PEP written and implemented by Ben Hoyt with the help of Victor Stinner.</dd>
</dl>
</div>
</div>
<div class="section" id="pep-475-retry-system-calls-failing-with-eintr">
<h3>PEP 475: Retry system calls failing with EINTR<a class="headerlink" href="#pep-475-retry-system-calls-failing-with-eintr" title="Permalink to this headline">¶</a></h3>
An <a class="reference internal" href="../library/errno.html#errno.EINTR" title="errno.EINTR"><code class="xref py py-data docutils literal notranslate">errno.EINTR</code></a> error code is returned whenever a system call, that
is waiting for I/O, is interrupted by a signal. Previously, Python would
raise <a class="reference internal" href="../library/exceptions.html#InterruptedError" title="InterruptedError"><code class="xref py py-exc docutils literal notranslate">InterruptedError</code></a> in such cases. This meant that, when writing a
Python application, the developer had two choices:
<ol class="arabic simple">
<li>Ignore the <code class="docutils literal notranslate">InterruptedError</code>.</li>
<li>Handle the <code class="docutils literal notranslate">InterruptedError</code> and attempt to restart the interrupted
system call at every call site.</li>
</ol>
The first option makes an application fail intermittently.
The second option adds a large amount of boilerplate that makes the
code nearly unreadable. Compare:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>print(&quot;Hello World&quot;)
</pre></div>
</div>
and:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>while True:
 try:
 print(&quot;Hello World&quot;)
 break
 except InterruptedError:
 continue
</pre></div>
</div>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0475">PEP 475</a> implements automatic retry of system calls on
<code class="docutils literal notranslate">EINTR</code>. This removes the burden of dealing with <code class="docutils literal notranslate">EINTR</code>
or <a class="reference internal" href="../library/exceptions.html#InterruptedError" title="InterruptedError"><code class="xref py py-exc docutils literal notranslate">InterruptedError</code></a> in user code in most situations and makes
Python programs, including the standard library, more robust. Note that
the system call is only retried if the signal handler does not raise an
exception.
Below is a list of functions which are now retried when interrupted
by a signal:
<ul class="simple">
<li><a class="reference internal" href="../library/functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> and <a class="reference internal" href="../library/io.html#io.open" title="io.open"><code class="xref py py-func docutils literal notranslate">io.open()</code></a>;</li>
<li>functions of the <a class="reference internal" href="../library/faulthandler.html#module-faulthandler" title="faulthandler: Dump the Python traceback."><code class="xref py py-mod docutils literal notranslate">faulthandler</code></a> module;</li>
<li><a class="reference internal" href="../library/os.html#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal notranslate">os</code></a> functions: <a class="reference internal" href="../library/os.html#os.fchdir" title="os.fchdir"><code class="xref py py-func docutils literal notranslate">fchdir()</code></a>, <a class="reference internal" href="../library/os.html#os.fchmod" title="os.fchmod"><code class="xref py py-func docutils literal notranslate">fchmod()</code></a>,
<a class="reference internal" href="../library/os.html#os.fchown" title="os.fchown"><code class="xref py py-func docutils literal notranslate">fchown()</code></a>, <a class="reference internal" href="../library/os.html#os.fdatasync" title="os.fdatasync"><code class="xref py py-func docutils literal notranslate">fdatasync()</code></a>, <a class="reference internal" href="../library/os.html#os.fstat" title="os.fstat"><code class="xref py py-func docutils literal notranslate">fstat()</code></a>,
<a class="reference internal" href="../library/os.html#os.fstatvfs" title="os.fstatvfs"><code class="xref py py-func docutils literal notranslate">fstatvfs()</code></a>, <a class="reference internal" href="../library/os.html#os.fsync" title="os.fsync"><code class="xref py py-func docutils literal notranslate">fsync()</code></a>, <a class="reference internal" href="../library/os.html#os.ftruncate" title="os.ftruncate"><code class="xref py py-func docutils literal notranslate">ftruncate()</code></a>,
<a class="reference internal" href="../library/os.html#os.mkfifo" title="os.mkfifo"><code class="xref py py-func docutils literal notranslate">mkfifo()</code></a>, <a class="reference internal" href="../library/os.html#os.mknod" title="os.mknod"><code class="xref py py-func docutils literal notranslate">mknod()</code></a>, <a class="reference internal" href="../library/os.html#os.open" title="os.open"><code class="xref py py-func docutils literal notranslate">open()</code></a>,
<a class="reference internal" href="../library/os.html#os.posix_fadvise" title="os.posix_fadvise"><code class="xref py py-func docutils literal notranslate">posix_fadvise()</code></a>, <a class="reference internal" href="../library/os.html#os.posix_fallocate" title="os.posix_fallocate"><code class="xref py py-func docutils literal notranslate">posix_fallocate()</code></a>, <a class="reference internal" href="../library/os.html#os.pread" title="os.pread"><code class="xref py py-func docutils literal notranslate">pread()</code></a>,
<a class="reference internal" href="../library/os.html#os.pwrite" title="os.pwrite"><code class="xref py py-func docutils literal notranslate">pwrite()</code></a>, <a class="reference internal" href="../library/os.html#os.read" title="os.read"><code class="xref py py-func docutils literal notranslate">read()</code></a>, <a class="reference internal" href="../library/os.html#os.readv" title="os.readv"><code class="xref py py-func docutils literal notranslate">readv()</code></a>, <a class="reference internal" href="../library/os.html#os.sendfile" title="os.sendfile"><code class="xref py py-func docutils literal notranslate">sendfile()</code></a>,
<a class="reference internal" href="../library/os.html#os.wait3" title="os.wait3"><code class="xref py py-func docutils literal notranslate">wait3()</code></a>, <a class="reference internal" href="../library/os.html#os.wait4" title="os.wait4"><code class="xref py py-func docutils literal notranslate">wait4()</code></a>, <a class="reference internal" href="../library/os.html#os.wait" title="os.wait"><code class="xref py py-func docutils literal notranslate">wait()</code></a>,
<a class="reference internal" href="../library/os.html#os.waitid" title="os.waitid"><code class="xref py py-func docutils literal notranslate">waitid()</code></a>, <a class="reference internal" href="../library/os.html#os.waitpid" title="os.waitpid"><code class="xref py py-func docutils literal notranslate">waitpid()</code></a>, <a class="reference internal" href="../library/os.html#os.write" title="os.write"><code class="xref py py-func docutils literal notranslate">write()</code></a>,
<a class="reference internal" href="../library/os.html#os.writev" title="os.writev"><code class="xref py py-func docutils literal notranslate">writev()</code></a>;</li>
<li>special cases: <a class="reference internal" href="../library/os.html#os.close" title="os.close"><code class="xref py py-func docutils literal notranslate">os.close()</code></a> and <a class="reference internal" href="../library/os.html#os.dup2" title="os.dup2"><code class="xref py py-func docutils literal notranslate">os.dup2()</code></a> now ignore
<a class="reference internal" href="../library/errno.html#errno.EINTR" title="errno.EINTR"><code class="xref py py-data docutils literal notranslate">EINTR</code></a> errors; the syscall is not retried (see the PEP
for the rationale);</li>
<li><a class="reference internal" href="../library/select.html#module-select" title="select: Wait for I/O completion on multiple streams."><code class="xref py py-mod docutils literal notranslate">select</code></a> functions: <a class="reference internal" href="../library/select.html#select.devpoll.poll" title="select.devpoll.poll"><code class="xref py py-func docutils literal notranslate">devpoll.poll()</code></a>,
<a class="reference internal" href="../library/select.html#select.epoll.poll" title="select.epoll.poll"><code class="xref py py-func docutils literal notranslate">epoll.poll()</code></a>,
<a class="reference internal" href="../library/select.html#select.kqueue.control" title="select.kqueue.control"><code class="xref py py-func docutils literal notranslate">kqueue.control()</code></a>,
<a class="reference internal" href="../library/select.html#select.poll.poll" title="select.poll.poll"><code class="xref py py-func docutils literal notranslate">poll.poll()</code></a>, <a class="reference internal" href="../library/select.html#select.select" title="select.select"><code class="xref py py-func docutils literal notranslate">select()</code></a>;</li>
<li>methods of the <a class="reference internal" href="../library/socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate">socket</code></a> class: <a class="reference internal" href="../library/socket.html#socket.socket.accept" title="socket.socket.accept"><code class="xref py py-meth docutils literal notranslate">accept()</code></a>,
<a class="reference internal" href="../library/socket.html#socket.socket.connect" title="socket.socket.connect"><code class="xref py py-meth docutils literal notranslate">connect()</code></a> (except for non-blocking sockets),
<a class="reference internal" href="../library/socket.html#socket.socket.recv" title="socket.socket.recv"><code class="xref py py-meth docutils literal notranslate">recv()</code></a>, <a class="reference internal" href="../library/socket.html#socket.socket.recvfrom" title="socket.socket.recvfrom"><code class="xref py py-meth docutils literal notranslate">recvfrom()</code></a>,
<a class="reference internal" href="../library/socket.html#socket.socket.recvmsg" title="socket.socket.recvmsg"><code class="xref py py-meth docutils literal notranslate">recvmsg()</code></a>, <a class="reference internal" href="../library/socket.html#socket.socket.send" title="socket.socket.send"><code class="xref py py-meth docutils literal notranslate">send()</code></a>,
<a class="reference internal" href="../library/socket.html#socket.socket.sendall" title="socket.socket.sendall"><code class="xref py py-meth docutils literal notranslate">sendall()</code></a>, <a class="reference internal" href="../library/socket.html#socket.socket.sendmsg" title="socket.socket.sendmsg"><code class="xref py py-meth docutils literal notranslate">sendmsg()</code></a>,
<a class="reference internal" href="../library/socket.html#socket.socket.sendto" title="socket.socket.sendto"><code class="xref py py-meth docutils literal notranslate">sendto()</code></a>;</li>
<li><a class="reference internal" href="../library/signal.html#signal.sigtimedwait" title="signal.sigtimedwait"><code class="xref py py-func docutils literal notranslate">signal.sigtimedwait()</code></a> and <a class="reference internal" href="../library/signal.html#signal.sigwaitinfo" title="signal.sigwaitinfo"><code class="xref py py-func docutils literal notranslate">signal.sigwaitinfo()</code></a>;</li>
<li><a class="reference internal" href="../library/time.html#time.sleep" title="time.sleep"><code class="xref py py-func docutils literal notranslate">time.sleep()</code></a>.</li>
</ul>
<div class="admonition seealso">
See also
<dl class="last docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0475">PEP 475</a> – Retry system calls failing with EINTR</dt>
<dd>PEP and implementation written by Charles-François Natali and
Victor Stinner, with the help of Antoine Pitrou (the French connection).</dd>
</dl>
</div>
</div>
<div class="section" id="pep-479-change-stopiteration-handling-inside-generators">
<h3>PEP 479: Change StopIteration handling inside generators<a class="headerlink" href="#pep-479-change-stopiteration-handling-inside-generators" title="Permalink to this headline">¶</a></h3>
The interaction of generators and <a class="reference internal" href="../library/exceptions.html#StopIteration" title="StopIteration"><code class="xref py py-exc docutils literal notranslate">StopIteration</code></a> in Python 3.4 and
earlier was sometimes surprising, and could conceal obscure bugs. Previously,
<code class="docutils literal notranslate">StopIteration</code> raised accidentally inside a generator function was
interpreted as the end of the iteration by the loop construct driving the
generator.
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0479">PEP 479</a> changes the behavior of generators: when a <code class="docutils literal notranslate">StopIteration</code>
exception is raised inside a generator, it is replaced with a
<a class="reference internal" href="../library/exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate">RuntimeError</code></a> before it exits the generator frame. The main goal of
this change is to ease debugging in the situation where an unguarded
<a class="reference internal" href="../library/functions.html#next" title="next"><code class="xref py py-func docutils literal notranslate">next()</code></a> call raises <code class="docutils literal notranslate">StopIteration</code> and causes the iteration controlled
by the generator to terminate silently. This is particularly pernicious in
combination with the <code class="docutils literal notranslate">yield from</code> construct.
This is a backwards incompatible change, so to enable the new behavior,
a <a class="reference internal" href="../glossary.html#term-future">__future__</a> import is necessary:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; from __future__ import generator_stop

&gt;&gt;&gt; def gen():
... next(iter([]))
... yield
...
&gt;&gt;&gt; next(gen())
Traceback (most recent call last):
 File &quot;&lt;stdin&gt;&quot;, line 2, in gen
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
 File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
RuntimeError: generator raised StopIteration
</pre></div>
</div>
Without a <code class="docutils literal notranslate">__future__</code> import, a <a class="reference internal" href="../library/exceptions.html#PendingDeprecationWarning" title="PendingDeprecationWarning"><code class="xref py py-exc docutils literal notranslate">PendingDeprecationWarning</code></a> will be
raised whenever a <code class="docutils literal notranslate">StopIteration</code> exception is raised inside a generator.
<div class="admonition seealso">
See also
<dl class="last docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0479">PEP 479</a> – Change StopIteration handling inside generators</dt>
<dd>PEP written by Chris Angelico and Guido van Rossum. Implemented by
Chris Angelico, Yury Selivanov and Nick Coghlan.</dd>
</dl>
</div>
</div>
<div class="section" id="pep-485-a-function-for-testing-approximate-equality">
<h3>PEP 485: A function for testing approximate equality<a class="headerlink" href="#pep-485-a-function-for-testing-approximate-equality" title="Permalink to this headline">¶</a></h3>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0485">PEP 485</a> adds the <a class="reference internal" href="../library/math.html#math.isclose" title="math.isclose"><code class="xref py py-func docutils literal notranslate">math.isclose()</code></a> and <a class="reference internal" href="../library/cmath.html#cmath.isclose" title="cmath.isclose"><code class="xref py py-func docutils literal notranslate">cmath.isclose()</code></a>
functions which tell whether two values are approximately equal or
“close” to each other. Whether or not two values are considered
close is determined according to given absolute and relative tolerances.
Relative tolerance is the maximum allowed difference between <code class="docutils literal notranslate">isclose</code>
arguments, relative to the larger absolute value:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import math
&gt;&gt;&gt; a = 5.0
&gt;&gt;&gt; b = 4.99998
&gt;&gt;&gt; math.isclose(a, b, rel_tol=1e-5)
True
&gt;&gt;&gt; math.isclose(a, b, rel_tol=1e-6)
False
</pre></div>
</div>
It is also possible to compare two values using absolute tolerance, which
must be a non-negative value:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import math
&gt;&gt;&gt; a = 5.0
&gt;&gt;&gt; b = 4.99998
&gt;&gt;&gt; math.isclose(a, b, abs_tol=0.00003)
True
&gt;&gt;&gt; math.isclose(a, b, abs_tol=0.00001)
False
</pre></div>
</div>
<div class="admonition seealso">
See also
<dl class="last docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0485">PEP 485</a> – A function for testing approximate equality</dt>
<dd>PEP written by Christopher Barker; implemented by Chris Barker and
Tal Einat.</dd>
</dl>
</div>
</div>
<div class="section" id="pep-486-make-the-python-launcher-aware-of-virtual-environments">
<h3>PEP 486: Make the Python Launcher aware of virtual environments<a class="headerlink" href="#pep-486-make-the-python-launcher-aware-of-virtual-environments" title="Permalink to this headline">¶</a></h3>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0486">PEP 486</a> makes the Windows launcher (see <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0397">PEP 397</a>) aware of an active
virtual environment. When the default interpreter would be used and the
<code class="docutils literal notranslate">VIRTUAL_ENV</code> environment variable is set, the interpreter in the virtual
environment will be used.
<div class="admonition seealso">
See also
<dl class="last docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0486">PEP 486</a> – Make the Python Launcher aware of virtual environments</dt>
<dd>PEP written and implemented by Paul Moore.</dd>
</dl>
</div>
</div>
<div class="section" id="pep-488-elimination-of-pyo-files">
<h3>PEP 488: Elimination of PYO files<a class="headerlink" href="#pep-488-elimination-of-pyo-files" title="Permalink to this headline">¶</a></h3>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0488">PEP 488</a> does away with the concept of <code class="docutils literal notranslate">.pyo</code> files. This means that
<code class="docutils literal notranslate">.pyc</code> files represent both unoptimized and optimized bytecode. To prevent the
need to constantly regenerate bytecode files, <code class="docutils literal notranslate">.pyc</code> files now have an
optional <code class="docutils literal notranslate">opt-</code> tag in their name when the bytecode is optimized. This has the
side-effect of no more bytecode file name clashes when running under either
<a class="reference internal" href="../using/cmdline.html#cmdoption-o"><code class="xref std std-option docutils literal notranslate">-O</code></a> or <a class="reference internal" href="../using/cmdline.html#cmdoption-oo"><code class="xref std std-option docutils literal notranslate">-OO</code></a>. Consequently, bytecode files generated from
<a class="reference internal" href="../using/cmdline.html#cmdoption-o"><code class="xref std std-option docutils literal notranslate">-O</code></a>, and <a class="reference internal" href="../using/cmdline.html#cmdoption-oo"><code class="xref std std-option docutils literal notranslate">-OO</code></a> may now exist simultaneously.
<a class="reference internal" href="../library/importlib.html#importlib.util.cache_from_source" title="importlib.util.cache_from_source"><code class="xref py py-func docutils literal notranslate">importlib.util.cache_from_source()</code></a> has an updated API to help with
this change.
<div class="admonition seealso">
See also
<dl class="last docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0488">PEP 488</a> – Elimination of PYO files</dt>
<dd>PEP written and implemented by Brett Cannon.</dd>
</dl>
</div>
</div>
<div class="section" id="pep-489-multi-phase-extension-module-initialization">
<h3>PEP 489: Multi-phase extension module initialization<a class="headerlink" href="#pep-489-multi-phase-extension-module-initialization" title="Permalink to this headline">¶</a></h3>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0489">PEP 489</a> updates extension module initialization to take advantage of the
two step module loading mechanism introduced by <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0451">PEP 451</a> in Python 3.4.
This change brings the import semantics of extension modules that opt-in to
using the new mechanism much closer to those of Python source and bytecode
modules, including the ability to use any valid identifier as a module name,
rather than being restricted to ASCII.
<div class="admonition seealso">
See also
<dl class="last docutils">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0489">PEP 489</a> – Multi-phase extension module initialization</dt>
<dd>PEP written by Petr Viktorin, Stefan Behnel, and Nick Coghlan;
implemented by Petr Viktorin.</dd>
</dl>
</div>
</div>
</div>
<div class="section" id="other-language-changes">
<h2>Other Language Changes<a class="headerlink" href="#other-language-changes" title="Permalink to this headline">¶</a></h2>
Some smaller changes made to the core Python language are:
<ul class="simple">
<li>Added the <code class="docutils literal notranslate">&quot;namereplace&quot;</code> error handlers. The <code class="docutils literal notranslate">&quot;backslashreplace&quot;</code>
error handlers now work with decoding and translating.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue19676">bpo-19676</a> and <a class="reference external" href="https://bugs.python.org/issue22286">bpo-22286</a>.)</li>
<li>The <a class="reference internal" href="../using/cmdline.html#cmdoption-b"><code class="xref std std-option docutils literal notranslate">-b</code></a> option now affects comparisons of <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> with
<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue23681">bpo-23681</a>.)</li>
<li>New Kazakh <code class="docutils literal notranslate">kz1048</code> and Tajik <code class="docutils literal notranslate">koi8_t</code> <a class="reference internal" href="../library/codecs.html#standard-encodings">codecs</a>.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue22682">bpo-22682</a> and <a class="reference external" href="https://bugs.python.org/issue22681">bpo-22681</a>.)</li>
<li>Property docstrings are now writable. This is especially useful for
<a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate">collections.namedtuple()</code></a> docstrings.
(Contributed by Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue24064">bpo-24064</a>.)</li>
<li>Circular imports involving relative imports are now supported.
(Contributed by Brett Cannon and Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue17636">bpo-17636</a>.)</li>
</ul>
</div>
<div class="section" id="new-modules">
<h2>New Modules<a class="headerlink" href="#new-modules" title="Permalink to this headline">¶</a></h2>
<div class="section" id="typing">
<h3>typing<a class="headerlink" href="#typing" title="Permalink to this headline">¶</a></h3>
The new <a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see PEP 484)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> <a class="reference internal" href="../glossary.html#term-provisional-api">provisional</a> module
provides standard definitions and tools for function type annotations.
See <a class="reference internal" href="#whatsnew-pep-484">Type Hints</a> for more information.
</div>
<div class="section" id="zipapp">
<h3>zipapp<a class="headerlink" href="#zipapp" title="Permalink to this headline">¶</a></h3>
The new <a class="reference internal" href="../library/zipapp.html#module-zipapp" title="zipapp: Manage executable python zip archives"><code class="xref py py-mod docutils literal notranslate">zipapp</code></a> module (specified in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0441">PEP 441</a>) provides an API and
command line tool for creating executable Python Zip Applications, which
were introduced in Python 2.6 in <a class="reference external" href="https://bugs.python.org/issue1739468">bpo-1739468</a>, but which were not well
publicized, either at the time or since.
With the new module, bundling your application is as simple as putting all
the files, including a <code class="docutils literal notranslate">__main__.py</code> file, into a directory <code class="docutils literal notranslate">myapp</code>
and running:
<div class="highlight-shell-session notranslate"><div class="highlight"><pre>$ python -m zipapp myapp
$ python myapp.pyz
</pre></div>
</div>
The module implementation has been contributed by Paul Moore in
<a class="reference external" href="https://bugs.python.org/issue23491">bpo-23491</a>.
<div class="admonition seealso">
See also
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0441">PEP 441</a> – Improving Python ZIP Application Support
</div>
</div>
</div>
<div class="section" id="improved-modules">
<h2>Improved Modules<a class="headerlink" href="#improved-modules" title="Permalink to this headline">¶</a></h2>
<div class="section" id="argparse">
<h3>argparse<a class="headerlink" href="#argparse" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/argparse.html#argparse.ArgumentParser" title="argparse.ArgumentParser"><code class="xref py py-class docutils literal notranslate">ArgumentParser</code></a> class now allows disabling
<a class="reference internal" href="../library/argparse.html#prefix-matching">abbreviated usage</a> of long options by setting
<a class="reference internal" href="../library/argparse.html#allow-abbrev">allow_abbrev</a> to <code class="docutils literal notranslate">False</code>. (Contributed by Jonathan Paugh,
Steven Bethard, paul j3 and Daniel Eriksson in <a class="reference external" href="https://bugs.python.org/issue14910">bpo-14910</a>.)
</div>
<div class="section" id="asyncio">
<h3>asyncio<a class="headerlink" href="#asyncio" title="Permalink to this headline">¶</a></h3>
Since the <a class="reference internal" href="../library/asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O, event loop, coroutines and tasks."><code class="xref py py-mod docutils literal notranslate">asyncio</code></a> module is <a class="reference internal" href="../glossary.html#term-provisional-api">provisional</a>,
all changes introduced in Python 3.5 have also been backported to Python 3.4.x.
Notable changes in the <a class="reference internal" href="../library/asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O, event loop, coroutines and tasks."><code class="xref py py-mod docutils literal notranslate">asyncio</code></a> module since Python 3.4.0:
<ul class="simple">
<li>New debugging APIs: <code class="xref py py-meth docutils literal notranslate">loop.set_debug()</code>
and <code class="xref py py-meth docutils literal notranslate">loop.get_debug()</code> methods.
(Contributed by Victor Stinner.)</li>
<li>The proactor event loop now supports SSL.
(Contributed by Antoine Pitrou and Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue22560">bpo-22560</a>.)</li>
<li>A new <code class="xref py py-meth docutils literal notranslate">loop.is_closed()</code> method to
check if the event loop is closed.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue21326">bpo-21326</a>.)</li>
<li>A new <code class="xref py py-meth docutils literal notranslate">loop.create_task()</code>
to conveniently create and schedule a new <a class="reference internal" href="../library/asyncio-task.html#asyncio.Task" title="asyncio.Task"><code class="xref py py-class docutils literal notranslate">Task</code></a>
for a coroutine. The <code class="docutils literal notranslate">create_task</code> method is also used by all
asyncio functions that wrap coroutines into tasks, such as
<a class="reference internal" href="../library/asyncio-task.html#asyncio.wait" title="asyncio.wait"><code class="xref py py-func docutils literal notranslate">asyncio.wait()</code></a>, <a class="reference internal" href="../library/asyncio-task.html#asyncio.gather" title="asyncio.gather"><code class="xref py py-func docutils literal notranslate">asyncio.gather()</code></a>, etc.
(Contributed by Victor Stinner.)</li>
<li>A new <a class="reference internal" href="../library/asyncio-protocol.html#asyncio.WriteTransport.get_write_buffer_limits" title="asyncio.WriteTransport.get_write_buffer_limits"><code class="xref py py-meth docutils literal notranslate">transport.get_write_buffer_limits()</code></a>
method to inquire for high- and low- water limits of the flow
control.
(Contributed by Victor Stinner.)</li>
<li>The <a class="reference internal" href="../library/asyncio-task.html#asyncio.async" title="asyncio.async"><code class="xref py py-func docutils literal notranslate">async()</code></a> function is deprecated in favor of
<a class="reference internal" href="../library/asyncio-task.html#asyncio.ensure_future" title="asyncio.ensure_future"><code class="xref py py-func docutils literal notranslate">ensure_future()</code></a>.
(Contributed by Yury Selivanov.)</li>
<li>New <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.AbstractEventLoop.set_task_factory" title="asyncio.AbstractEventLoop.set_task_factory"><code class="xref py py-meth docutils literal notranslate">loop.set_task_factory()</code></a> and
<a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.AbstractEventLoop.get_task_factory" title="asyncio.AbstractEventLoop.get_task_factory"><code class="xref py py-meth docutils literal notranslate">loop.get_task_factory()</code></a>
methods to customize the task factory that <code class="xref py py-meth docutils literal notranslate">loop.create_task()</code> method uses. (Contributed by Yury
Selivanov.)</li>
<li>New <a class="reference internal" href="../library/asyncio-queue.html#asyncio.Queue.join" title="asyncio.Queue.join"><code class="xref py py-meth docutils literal notranslate">Queue.join()</code></a> and
<a class="reference internal" href="../library/asyncio-queue.html#asyncio.Queue.task_done" title="asyncio.Queue.task_done"><code class="xref py py-meth docutils literal notranslate">Queue.task_done()</code></a> queue methods.
(Contributed by Victor Stinner.)</li>
<li>The <code class="docutils literal notranslate">JoinableQueue</code> class was removed, in favor of the
<a class="reference internal" href="../library/asyncio-queue.html#asyncio.Queue" title="asyncio.Queue"><code class="xref py py-class docutils literal notranslate">asyncio.Queue</code></a> class.
(Contributed by Victor Stinner.)</li>
</ul>
Updates in 3.5.1:
<ul class="simple">
<li>The <a class="reference internal" href="../library/asyncio-task.html#asyncio.ensure_future" title="asyncio.ensure_future"><code class="xref py py-func docutils literal notranslate">ensure_future()</code></a> function and all functions that
use it, such as <code class="xref py py-meth docutils literal notranslate">loop.run_until_complete()</code>,
now accept all kinds of <a class="reference internal" href="../glossary.html#term-awaitable">awaitable objects</a>.
(Contributed by Yury Selivanov.)</li>
<li>New <a class="reference internal" href="../library/asyncio-task.html#asyncio.run_coroutine_threadsafe" title="asyncio.run_coroutine_threadsafe"><code class="xref py py-func docutils literal notranslate">run_coroutine_threadsafe()</code></a> function to submit
coroutines to event loops from other threads.
(Contributed by Vincent Michel.)</li>
<li>New <a class="reference internal" href="../library/asyncio-protocol.html#asyncio.BaseTransport.is_closing" title="asyncio.BaseTransport.is_closing"><code class="xref py py-meth docutils literal notranslate">Transport.is_closing()</code></a>
method to check if the transport is closing or closed.
(Contributed by Yury Selivanov.)</li>
<li>The <code class="xref py py-meth docutils literal notranslate">loop.create_server()</code>
method can now accept a list of hosts.
(Contributed by Yann Sionneau.)</li>
</ul>
Updates in 3.5.2:
<ul class="simple">
<li>New <code class="xref py py-meth docutils literal notranslate">loop.create_future()</code>
method to create Future objects. This allows alternative event
loop implementations, such as
<a class="reference external" href="https://github.com/MagicStack/uvloop">uvloop</a>, to provide a faster
<a class="reference internal" href="../library/asyncio-task.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate">asyncio.Future</code></a> implementation.
(Contributed by Yury Selivanov.)</li>
<li>New <code class="xref py py-meth docutils literal notranslate">loop.get_exception_handler()</code>
method to get the current exception handler.
(Contributed by Yury Selivanov.)</li>
<li>New <a class="reference internal" href="../library/asyncio-stream.html#asyncio.StreamReader.readuntil" title="asyncio.StreamReader.readuntil"><code class="xref py py-meth docutils literal notranslate">StreamReader.readuntil()</code></a>
method to read data from the stream until a separator bytes
sequence appears.
(Contributed by Mark Korenberg.)</li>
<li>The <code class="xref py py-meth docutils literal notranslate">loop.create_connection()</code>
and <code class="xref py py-meth docutils literal notranslate">loop.create_server()</code>
methods are optimized to avoid calling the system <code class="docutils literal notranslate">getaddrinfo</code>
function if the address is already resolved.
(Contributed by A. Jesse Jiryu Davis.)</li>
<li>The <code class="xref py py-meth docutils literal notranslate">loop.sock_connect(sock, address)</code>
no longer requires the address to be resolved prior to the call.
(Contributed by A. Jesse Jiryu Davis.)</li>
</ul>
</div>
<div class="section" id="bz2">
<h3>bz2<a class="headerlink" href="#bz2" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/bz2.html#bz2.BZ2Decompressor.decompress" title="bz2.BZ2Decompressor.decompress"><code class="xref py py-meth docutils literal notranslate">BZ2Decompressor.decompress</code></a>
method now accepts an optional max_length argument to limit the maximum
size of decompressed data. (Contributed by Nikolaus Rath in <a class="reference external" href="https://bugs.python.org/issue15955">bpo-15955</a>.)
</div>
<div class="section" id="cgi">
<h3>cgi<a class="headerlink" href="#cgi" title="Permalink to this headline">¶</a></h3>
The <code class="xref py py-class docutils literal notranslate">FieldStorage</code> class now supports the <a class="reference internal" href="../glossary.html#term-context-manager">context manager</a>
protocol. (Contributed by Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue20289">bpo-20289</a>.)
</div>
<div class="section" id="cmath">
<h3>cmath<a class="headerlink" href="#cmath" title="Permalink to this headline">¶</a></h3>
A new function <a class="reference internal" href="../library/cmath.html#cmath.isclose" title="cmath.isclose"><code class="xref py py-func docutils literal notranslate">isclose()</code></a> provides a way to test for approximate
equality. (Contributed by Chris Barker and Tal Einat in <a class="reference external" href="https://bugs.python.org/issue24270">bpo-24270</a>.)
</div>
<div class="section" id="code">
<h3>code<a class="headerlink" href="#code" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/code.html#code.InteractiveInterpreter.showtraceback" title="code.InteractiveInterpreter.showtraceback"><code class="xref py py-func docutils literal notranslate">InteractiveInterpreter.showtraceback()</code></a>
method now prints the full chained traceback, just like the interactive
interpreter. (Contributed by Claudiu Popa in <a class="reference external" href="https://bugs.python.org/issue17442">bpo-17442</a>.)
</div>
<div class="section" id="collections">
<h3>collections<a class="headerlink" href="#collections" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate">OrderedDict</code></a> class is now implemented in C, which
makes it 4 to 100 times faster. (Contributed by Eric Snow in <a class="reference external" href="https://bugs.python.org/issue16991">bpo-16991</a>.)
<code class="xref py py-meth docutils literal notranslate">OrderedDict.items()</code>,
<code class="xref py py-meth docutils literal notranslate">OrderedDict.keys()</code>,
<code class="xref py py-meth docutils literal notranslate">OrderedDict.values()</code> views now support
<a class="reference internal" href="../library/functions.html#reversed" title="reversed"><code class="xref py py-func docutils literal notranslate">reversed()</code></a> iteration.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue19505">bpo-19505</a>.)
The <a class="reference internal" href="../library/collections.html#collections.deque" title="collections.deque"><code class="xref py py-class docutils literal notranslate">deque</code></a> class now defines
<a class="reference internal" href="../library/collections.html#collections.deque.index" title="collections.deque.index"><code class="xref py py-meth docutils literal notranslate">index()</code></a>, <a class="reference internal" href="../library/collections.html#collections.deque.insert" title="collections.deque.insert"><code class="xref py py-meth docutils literal notranslate">insert()</code></a>, and
<a class="reference internal" href="../library/collections.html#collections.deque.copy" title="collections.deque.copy"><code class="xref py py-meth docutils literal notranslate">copy()</code></a>, and supports the <code class="docutils literal notranslate">+</code> and <code class="docutils literal notranslate">*</code> operators.
This allows deques to be recognized as a <a class="reference internal" href="../library/collections.abc.html#collections.abc.MutableSequence" title="collections.abc.MutableSequence"><code class="xref py py-class docutils literal notranslate">MutableSequence</code></a>
and improves their substitutability for lists.
(Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue23704">bpo-23704</a>.)
Docstrings produced by <a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate">namedtuple()</code></a> can now be updated:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Point = namedtuple(&#39;Point&#39;, [&#39;x&#39;, &#39;y&#39;])
Point.__doc__ += &#39;: Cartesian coodinate&#39;
Point.x.__doc__ = &#39;abscissa&#39;
Point.y.__doc__ = &#39;ordinate&#39;
</pre></div>
</div>
(Contributed by Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue24064">bpo-24064</a>.)
The <a class="reference internal" href="../library/collections.html#collections.UserString" title="collections.UserString"><code class="xref py py-class docutils literal notranslate">UserString</code></a> class now implements the
<a class="reference internal" href="../library/pickle.html#object.__getnewargs__" title="object.__getnewargs__"><code class="xref py py-meth docutils literal notranslate">__getnewargs__()</code></a>, <a class="reference internal" href="../reference/datamodel.html#object.__rmod__" title="object.__rmod__"><code class="xref py py-meth docutils literal notranslate">__rmod__()</code></a>, <a class="reference internal" href="../library/stdtypes.html#str.casefold" title="str.casefold"><code class="xref py py-meth docutils literal notranslate">casefold()</code></a>,
<a class="reference internal" href="../library/stdtypes.html#str.format_map" title="str.format_map"><code class="xref py py-meth docutils literal notranslate">format_map()</code></a>, <a class="reference internal" href="../library/stdtypes.html#str.isprintable" title="str.isprintable"><code class="xref py py-meth docutils literal notranslate">isprintable()</code></a>, and <a class="reference internal" href="../library/stdtypes.html#str.maketrans" title="str.maketrans"><code class="xref py py-meth docutils literal notranslate">maketrans()</code></a>
methods to match the corresponding methods of <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>.
(Contributed by Joe Jevnik in <a class="reference external" href="https://bugs.python.org/issue22189">bpo-22189</a>.)
</div>
<div class="section" id="collections-abc">
<h3>collections.abc<a class="headerlink" href="#collections-abc" title="Permalink to this headline">¶</a></h3>
The <code class="xref py py-meth docutils literal notranslate">Sequence.index()</code> method now
accepts start and stop arguments to match the corresponding methods
of <a class="reference internal" href="../library/stdtypes.html#tuple" title="tuple"><code class="xref py py-class docutils literal notranslate">tuple</code></a>, <a class="reference internal" href="../library/stdtypes.html#list" title="list"><code class="xref py py-class docutils literal notranslate">list</code></a>, etc.
(Contributed by Devin Jeanpierre in <a class="reference external" href="https://bugs.python.org/issue23086">bpo-23086</a>.)
A new <a class="reference internal" href="../library/collections.abc.html#collections.abc.Generator" title="collections.abc.Generator"><code class="xref py py-class docutils literal notranslate">Generator</code></a> abstract base class. (Contributed
by Stefan Behnel in <a class="reference external" href="https://bugs.python.org/issue24018">bpo-24018</a>.)
New <a class="reference internal" href="../library/collections.abc.html#collections.abc.Awaitable" title="collections.abc.Awaitable"><code class="xref py py-class docutils literal notranslate">Awaitable</code></a>, <a class="reference internal" href="../library/collections.abc.html#collections.abc.Coroutine" title="collections.abc.Coroutine"><code class="xref py py-class docutils literal notranslate">Coroutine</code></a>,
<a class="reference internal" href="../library/collections.abc.html#collections.abc.AsyncIterator" title="collections.abc.AsyncIterator"><code class="xref py py-class docutils literal notranslate">AsyncIterator</code></a>, and
<a class="reference internal" href="../library/collections.abc.html#collections.abc.AsyncIterable" title="collections.abc.AsyncIterable"><code class="xref py py-class docutils literal notranslate">AsyncIterable</code></a> abstract base classes.
(Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue24184">bpo-24184</a>.)
For earlier Python versions, a backport of the new ABCs is available in an
external <a class="reference external" href="https://pypi.org/project/backports_abc">PyPI package</a>.
</div>
<div class="section" id="compileall">
<h3>compileall<a class="headerlink" href="#compileall" title="Permalink to this headline">¶</a></h3>
A new <a class="reference internal" href="../library/compileall.html#module-compileall" title="compileall: Tools for byte-compiling all Python source files in a directory tree."><code class="xref py py-mod docutils literal notranslate">compileall</code></a> option, <code class="samp docutils literal notranslate">-j N</code>, allows running N workers
simultaneously to perform parallel bytecode compilation.
The <a class="reference internal" href="../library/compileall.html#compileall.compile_dir" title="compileall.compile_dir"><code class="xref py py-func docutils literal notranslate">compile_dir()</code></a> function has a corresponding <code class="docutils literal notranslate">workers</code>
parameter. (Contributed by Claudiu Popa in <a class="reference external" href="https://bugs.python.org/issue16104">bpo-16104</a>.)
Another new option, <code class="docutils literal notranslate">-r</code>, allows controlling the maximum recursion
level for subdirectories. (Contributed by Claudiu Popa in <a class="reference external" href="https://bugs.python.org/issue19628">bpo-19628</a>.)
The <code class="docutils literal notranslate">-q</code> command line option can now be specified more than once, in
which case all output, including errors, will be suppressed. The corresponding
<code class="docutils literal notranslate">quiet</code> parameter in <a class="reference internal" href="../library/compileall.html#compileall.compile_dir" title="compileall.compile_dir"><code class="xref py py-func docutils literal notranslate">compile_dir()</code></a>,
<a class="reference internal" href="../library/compileall.html#compileall.compile_file" title="compileall.compile_file"><code class="xref py py-func docutils literal notranslate">compile_file()</code></a>, and <a class="reference internal" href="../library/compileall.html#compileall.compile_path" title="compileall.compile_path"><code class="xref py py-func docutils literal notranslate">compile_path()</code></a> can now
accept an integer value indicating the level of output suppression.
(Contributed by Thomas Kluyver in <a class="reference external" href="https://bugs.python.org/issue21338">bpo-21338</a>.)
</div>
<div class="section" id="concurrent-futures">
<h3>concurrent.futures<a class="headerlink" href="#concurrent-futures" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/concurrent.futures.html#concurrent.futures.Executor.map" title="concurrent.futures.Executor.map"><code class="xref py py-meth docutils literal notranslate">Executor.map()</code></a> method now accepts a
chunksize argument to allow batching of tasks to improve performance when
<a class="reference internal" href="../library/concurrent.futures.html#concurrent.futures.ProcessPoolExecutor" title="concurrent.futures.ProcessPoolExecutor"><code class="xref py py-meth docutils literal notranslate">ProcessPoolExecutor()</code></a> is used.
(Contributed by Dan O’Reilly in <a class="reference external" href="https://bugs.python.org/issue11271">bpo-11271</a>.)
The number of workers in the <a class="reference internal" href="../library/concurrent.futures.html#concurrent.futures.ThreadPoolExecutor" title="concurrent.futures.ThreadPoolExecutor"><code class="xref py py-class docutils literal notranslate">ThreadPoolExecutor</code></a>
constructor is optional now. The default value is 5 times the number of CPUs.
(Contributed by Claudiu Popa in <a class="reference external" href="https://bugs.python.org/issue21527">bpo-21527</a>.)
</div>
<div class="section" id="configparser">
<h3>configparser<a class="headerlink" href="#configparser" title="Permalink to this headline">¶</a></h3>
<a class="reference internal" href="../library/configparser.html#module-configparser" title="configparser: Configuration file parser."><code class="xref py py-mod docutils literal notranslate">configparser</code></a> now provides a way to customize the conversion
of values by specifying a dictionary of converters in the
<a class="reference internal" href="../library/configparser.html#configparser.ConfigParser" title="configparser.ConfigParser"><code class="xref py py-class docutils literal notranslate">ConfigParser</code></a> constructor, or by defining them
as methods in <code class="docutils literal notranslate">ConfigParser</code> subclasses. Converters defined in
a parser instance are inherited by its section proxies.
Example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import configparser
&gt;&gt;&gt; conv = {}
&gt;&gt;&gt; conv[&#39;list&#39;] = lambda v: [e.strip() for e in v.split() if e.strip()]
&gt;&gt;&gt; cfg = configparser.ConfigParser(converters=conv)
&gt;&gt;&gt; cfg.read_string(&quot;&quot;&quot;
... [s]
... list = a b c d e f g
... &quot;&quot;&quot;)
&gt;&gt;&gt; cfg.get(&#39;s&#39;, &#39;list&#39;)
&#39;a b c d e f g&#39;
&gt;&gt;&gt; cfg.getlist(&#39;s&#39;, &#39;list&#39;)
[&#39;a&#39;, &#39;b&#39;, &#39;c&#39;, &#39;d&#39;, &#39;e&#39;, &#39;f&#39;, &#39;g&#39;]
&gt;&gt;&gt; section = cfg[&#39;s&#39;]
&gt;&gt;&gt; section.getlist(&#39;list&#39;)
[&#39;a&#39;, &#39;b&#39;, &#39;c&#39;, &#39;d&#39;, &#39;e&#39;, &#39;f&#39;, &#39;g&#39;]
</pre></div>
</div>
(Contributed by Łukasz Langa in <a class="reference external" href="https://bugs.python.org/issue18159">bpo-18159</a>.)
</div>
<div class="section" id="contextlib">
<h3>contextlib<a class="headerlink" href="#contextlib" title="Permalink to this headline">¶</a></h3>
The new <a class="reference internal" href="../library/contextlib.html#contextlib.redirect_stderr" title="contextlib.redirect_stderr"><code class="xref py py-func docutils literal notranslate">redirect_stderr()</code></a> <a class="reference internal" href="../glossary.html#term-context-manager">context manager</a> (similar to
<a class="reference internal" href="../library/contextlib.html#contextlib.redirect_stdout" title="contextlib.redirect_stdout"><code class="xref py py-func docutils literal notranslate">redirect_stdout()</code></a>) makes it easier for utility scripts to
handle inflexible APIs that write their output to <a class="reference internal" href="../library/sys.html#sys.stderr" title="sys.stderr"><code class="xref py py-data docutils literal notranslate">sys.stderr</code></a> and
don’t provide any options to redirect it:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import contextlib, io, logging
&gt;&gt;&gt; f = io.StringIO()
&gt;&gt;&gt; with contextlib.redirect_stderr(f):
... logging.warning(&#39;warning&#39;)
...
&gt;&gt;&gt; f.getvalue()
&#39;WARNING:root:warning\n&#39;
</pre></div>
</div>
(Contributed by Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue22389">bpo-22389</a>.)
</div>
<div class="section" id="csv">
<h3>csv<a class="headerlink" href="#csv" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/csv.html#csv.csvwriter.writerow" title="csv.csvwriter.writerow"><code class="xref py py-meth docutils literal notranslate">writerow()</code></a> method now supports arbitrary iterables,
not just sequences. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue23171">bpo-23171</a>.)
</div>
<div class="section" id="curses">
<h3>curses<a class="headerlink" href="#curses" title="Permalink to this headline">¶</a></h3>
The new <a class="reference internal" href="../library/curses.html#curses.update_lines_cols" title="curses.update_lines_cols"><code class="xref py py-func docutils literal notranslate">update_lines_cols()</code></a> function updates the <code class="xref std std-envvar docutils literal notranslate">LINES</code>
and <code class="xref std std-envvar docutils literal notranslate">COLS</code> environment variables. This is useful for detecting
manual screen resizing. (Contributed by Arnon Yaari in <a class="reference external" href="https://bugs.python.org/issue4254">bpo-4254</a>.)
</div>
<div class="section" id="dbm">
<h3>dbm<a class="headerlink" href="#dbm" title="Permalink to this headline">¶</a></h3>
<a class="reference internal" href="../library/dbm.html#dbm.dumb.open" title="dbm.dumb.open"><code class="xref py py-func docutils literal notranslate">dumb.open</code></a> always creates a new database when the flag
has the value <code class="docutils literal notranslate">&quot;n&quot;</code>. (Contributed by Claudiu Popa in <a class="reference external" href="https://bugs.python.org/issue18039">bpo-18039</a>.)
</div>
<div class="section" id="difflib">
<h3>difflib<a class="headerlink" href="#difflib" title="Permalink to this headline">¶</a></h3>
The charset of HTML documents generated by
<a class="reference internal" href="../library/difflib.html#difflib.HtmlDiff.make_file" title="difflib.HtmlDiff.make_file"><code class="xref py py-meth docutils literal notranslate">HtmlDiff.make_file()</code></a>
can now be customized by using a new charset keyword-only argument.
The default charset of HTML document changed from <code class="docutils literal notranslate">&quot;ISO-8859-1&quot;</code>
to <code class="docutils literal notranslate">&quot;utf-8&quot;</code>.
(Contributed by Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue2052">bpo-2052</a>.)
The <a class="reference internal" href="../library/difflib.html#difflib.diff_bytes" title="difflib.diff_bytes"><code class="xref py py-func docutils literal notranslate">diff_bytes()</code></a> function can now compare lists of byte
strings. This fixes a regression from Python 2.
(Contributed by Terry J. Reedy and Greg Ward in <a class="reference external" href="https://bugs.python.org/issue17445">bpo-17445</a>.)
</div>
<div class="section" id="distutils">
<h3>distutils<a class="headerlink" href="#distutils" title="Permalink to this headline">¶</a></h3>
Both the <code class="docutils literal notranslate">build</code> and <code class="docutils literal notranslate">build_ext</code> commands now accept a <code class="docutils literal notranslate">-j</code> option to
enable parallel building of extension modules.
(Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue5309">bpo-5309</a>.)
The <a class="reference internal" href="../library/distutils.html#module-distutils" title="distutils: Support for building and installing Python modules into an existing Python installation."><code class="xref py py-mod docutils literal notranslate">distutils</code></a> module now supports <code class="docutils literal notranslate">xz</code> compression, and can be
enabled by passing <code class="docutils literal notranslate">xztar</code> as an argument to <code class="docutils literal notranslate">bdist --format</code>.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue16314">bpo-16314</a>.)
</div>
<div class="section" id="doctest">
<h3>doctest<a class="headerlink" href="#doctest" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/doctest.html#doctest.DocTestSuite" title="doctest.DocTestSuite"><code class="xref py py-func docutils literal notranslate">DocTestSuite()</code></a> function returns an empty
<a class="reference internal" href="../library/unittest.html#unittest.TestSuite" title="unittest.TestSuite"><code class="xref py py-class docutils literal notranslate">unittest.TestSuite</code></a> if module contains no docstrings, instead of
raising <a class="reference internal" href="../library/exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a>. (Contributed by Glenn Jones in <a class="reference external" href="https://bugs.python.org/issue15916">bpo-15916</a>.)
</div>
<div class="section" id="email">
<h3>email<a class="headerlink" href="#email" title="Permalink to this headline">¶</a></h3>
A new policy option <a class="reference internal" href="../library/email.policy.html#email.policy.Policy.mangle_from_" title="email.policy.Policy.mangle_from_"><code class="xref py py-attr docutils literal notranslate">Policy.mangle_from_</code></a>
controls whether or not lines that start with <code class="docutils literal notranslate">&quot;From &quot;</code> in email bodies are
prefixed with a <code class="docutils literal notranslate">&quot;&gt;&quot;</code> character by generators. The default is <code class="docutils literal notranslate">True</code> for
<a class="reference internal" href="../library/email.policy.html#email.policy.compat32" title="email.policy.compat32"><code class="xref py py-attr docutils literal notranslate">compat32</code></a> and <code class="docutils literal notranslate">False</code> for all other policies.
(Contributed by Milan Oberkirch in <a class="reference external" href="https://bugs.python.org/issue20098">bpo-20098</a>.)
A new
<a class="reference internal" href="../library/email.compat32-message.html#email.message.Message.get_content_disposition" title="email.message.Message.get_content_disposition"><code class="xref py py-meth docutils literal notranslate">Message.get_content_disposition()</code></a>
method provides easy access to a canonical value for the
Content-Disposition header.
(Contributed by Abhilash Raj in <a class="reference external" href="https://bugs.python.org/issue21083">bpo-21083</a>.)
A new policy option <a class="reference internal" href="../library/email.policy.html#email.policy.EmailPolicy.utf8" title="email.policy.EmailPolicy.utf8"><code class="xref py py-attr docutils literal notranslate">EmailPolicy.utf8</code></a>
can be set to <code class="docutils literal notranslate">True</code> to encode email headers using the UTF-8 charset instead
of using encoded words. This allows <code class="docutils literal notranslate">Messages</code> to be formatted according to
<a class="rfc reference external" href="https://tools.ietf.org/html/rfc6532.html">RFC 6532</a> and used with an SMTP server that supports the <a class="rfc reference external" href="https://tools.ietf.org/html/rfc6531.html">RFC 6531</a>
<code class="docutils literal notranslate">SMTPUTF8</code> extension. (Contributed by R. David Murray in
<a class="reference external" href="https://bugs.python.org/issue24211">bpo-24211</a>.)
The <a class="reference internal" href="../library/email.mime.html#email.mime.text.MIMEText" title="email.mime.text.MIMEText"><code class="xref py py-class docutils literal notranslate">mime.text.MIMEText</code></a> constructor now
accepts a <a class="reference internal" href="../library/email.charset.html#email.charset.Charset" title="email.charset.Charset"><code class="xref py py-class docutils literal notranslate">charset.Charset</code></a> instance.
(Contributed by Claude Paroz and Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue16324">bpo-16324</a>.)
</div>
<div class="section" id="enum">
<h3>enum<a class="headerlink" href="#enum" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/enum.html#enum.Enum" title="enum.Enum"><code class="xref py py-class docutils literal notranslate">Enum</code></a> callable has a new parameter start to
specify the initial number of enum values if only names are provided:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; Animal = enum.Enum(&#39;Animal&#39;, &#39;cat dog&#39;, start=10)
&gt;&gt;&gt; Animal.cat
&lt;Animal.cat: 10&gt;
&gt;&gt;&gt; Animal.dog
&lt;Animal.dog: 11&gt;
</pre></div>
</div>
(Contributed by Ethan Furman in <a class="reference external" href="https://bugs.python.org/issue21706">bpo-21706</a>.)
</div>
<div class="section" id="faulthandler">
<h3>faulthandler<a class="headerlink" href="#faulthandler" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/faulthandler.html#faulthandler.enable" title="faulthandler.enable"><code class="xref py py-func docutils literal notranslate">enable()</code></a>, <a class="reference internal" href="../library/faulthandler.html#faulthandler.register" title="faulthandler.register"><code class="xref py py-func docutils literal notranslate">register()</code></a>,
<a class="reference internal" href="../library/faulthandler.html#faulthandler.dump_traceback" title="faulthandler.dump_traceback"><code class="xref py py-func docutils literal notranslate">dump_traceback()</code></a> and
<a class="reference internal" href="../library/faulthandler.html#faulthandler.dump_traceback_later" title="faulthandler.dump_traceback_later"><code class="xref py py-func docutils literal notranslate">dump_traceback_later()</code></a> functions now accept file
descriptors in addition to file-like objects.
(Contributed by Wei Wu in <a class="reference external" href="https://bugs.python.org/issue23566">bpo-23566</a>.)
</div>
<div class="section" id="functools">
<h3>functools<a class="headerlink" href="#functools" title="Permalink to this headline">¶</a></h3>
Most of the <a class="reference internal" href="../library/functools.html#functools.lru_cache" title="functools.lru_cache"><code class="xref py py-func docutils literal notranslate">lru_cache()</code></a> machinery is now implemented in C, making
it significantly faster. (Contributed by Matt Joiner, Alexey Kachayev, and
Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue14373">bpo-14373</a>.)
</div>
<div class="section" id="glob">
<h3>glob<a class="headerlink" href="#glob" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/glob.html#glob.iglob" title="glob.iglob"><code class="xref py py-func docutils literal notranslate">iglob()</code></a> and <a class="reference internal" href="../library/glob.html#glob.glob" title="glob.glob"><code class="xref py py-func docutils literal notranslate">glob()</code></a> functions now support recursive
search in subdirectories, using the <code class="docutils literal notranslate">&quot;**&quot;</code> pattern.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue13968">bpo-13968</a>.)
</div>
<div class="section" id="gzip">
<h3>gzip<a class="headerlink" href="#gzip" title="Permalink to this headline">¶</a></h3>
The mode argument of the <a class="reference internal" href="../library/gzip.html#gzip.GzipFile" title="gzip.GzipFile"><code class="xref py py-class docutils literal notranslate">GzipFile</code></a> constructor now
accepts <code class="docutils literal notranslate">&quot;x&quot;</code> to request exclusive creation.
(Contributed by Tim Heaney in <a class="reference external" href="https://bugs.python.org/issue19222">bpo-19222</a>.)
</div>
<div class="section" id="heapq">
<h3>heapq<a class="headerlink" href="#heapq" title="Permalink to this headline">¶</a></h3>
Element comparison in <a class="reference internal" href="../library/heapq.html#heapq.merge" title="heapq.merge"><code class="xref py py-func docutils literal notranslate">merge()</code></a> can now be customized by
passing a <a class="reference internal" href="../glossary.html#term-key-function">key function</a> in a new optional key keyword argument,
and a new optional reverse keyword argument can be used to reverse element
comparison:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import heapq
&gt;&gt;&gt; a = [&#39;9&#39;, &#39;777&#39;, &#39;55555&#39;]
&gt;&gt;&gt; b = [&#39;88&#39;, &#39;6666&#39;]
&gt;&gt;&gt; list(heapq.merge(a, b, key=len))
[&#39;9&#39;, &#39;88&#39;, &#39;777&#39;, &#39;6666&#39;, &#39;55555&#39;]
&gt;&gt;&gt; list(heapq.merge(reversed(a), reversed(b), key=len, reverse=True))
[&#39;55555&#39;, &#39;6666&#39;, &#39;777&#39;, &#39;88&#39;, &#39;9&#39;]
</pre></div>
</div>
(Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue13742">bpo-13742</a>.)
</div>
<div class="section" id="http">
<h3>http<a class="headerlink" href="#http" title="Permalink to this headline">¶</a></h3>
A new <a class="reference internal" href="../library/http.html#http.HTTPStatus" title="http.HTTPStatus"><code class="xref py py-class docutils literal notranslate">HTTPStatus</code></a> enum that defines a set of
HTTP status codes, reason phrases and long descriptions written in English.
(Contributed by Demian Brecht in <a class="reference external" href="https://bugs.python.org/issue21793">bpo-21793</a>.)
</div>
<div class="section" id="http-client">
<h3>http.client<a class="headerlink" href="#http-client" title="Permalink to this headline">¶</a></h3>
<a class="reference internal" href="../library/http.client.html#http.client.HTTPConnection.getresponse" title="http.client.HTTPConnection.getresponse"><code class="xref py py-meth docutils literal notranslate">HTTPConnection.getresponse()</code></a>
now raises a <a class="reference internal" href="../library/http.client.html#http.client.RemoteDisconnected" title="http.client.RemoteDisconnected"><code class="xref py py-exc docutils literal notranslate">RemoteDisconnected</code></a> exception when a
remote server connection is closed unexpectedly. Additionally, if a
<a class="reference internal" href="../library/exceptions.html#ConnectionError" title="ConnectionError"><code class="xref py py-exc docutils literal notranslate">ConnectionError</code></a> (of which <code class="docutils literal notranslate">RemoteDisconnected</code>
is a subclass) is raised, the client socket is now closed automatically,
and will reconnect on the next request:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>import http.client
conn = http.client.HTTPConnection(&#39;www.python.org&#39;)
for retries in range(3):
 try:
 conn.request(&#39;GET&#39;, &#39;/&#39;)
 resp = conn.getresponse()
 except http.client.RemoteDisconnected:
 pass
</pre></div>
</div>
(Contributed by Martin Panter in <a class="reference external" href="https://bugs.python.org/issue3566">bpo-3566</a>.)
</div>
<div class="section" id="idlelib-and-idle">
<h3>idlelib and IDLE<a class="headerlink" href="#idlelib-and-idle" title="Permalink to this headline">¶</a></h3>
Since idlelib implements the IDLE shell and editor and is not intended for
import by other programs, it gets improvements with every release. See
<code class="file docutils literal notranslate">Lib/idlelib/NEWS.txt</code> for a cumulative list of changes since 3.4.0,
as well as changes made in future 3.5.x releases. This file is also available
from the IDLE Help ‣ About IDLE dialog.
</div>
<div class="section" id="imaplib">
<h3>imaplib<a class="headerlink" href="#imaplib" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/imaplib.html#imaplib.IMAP4" title="imaplib.IMAP4"><code class="xref py py-class docutils literal notranslate">IMAP4</code></a> class now supports the <a class="reference internal" href="../glossary.html#term-context-manager">context manager</a> protocol.
When used in a <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate">with</code></a> statement, the IMAP4 <code class="docutils literal notranslate">LOGOUT</code>
command will be called automatically at the end of the block.
(Contributed by Tarek Ziadé and Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue4972">bpo-4972</a>.)
The <a class="reference internal" href="../library/imaplib.html#module-imaplib" title="imaplib: IMAP4 protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">imaplib</code></a> module now supports <a class="rfc reference external" href="https://tools.ietf.org/html/rfc5161.html">RFC 5161</a> (ENABLE Extension)
and <a class="rfc reference external" href="https://tools.ietf.org/html/rfc6855.html">RFC 6855</a> (UTF-8 Support) via the <a class="reference internal" href="../library/imaplib.html#imaplib.IMAP4.enable" title="imaplib.IMAP4.enable"><code class="xref py py-meth docutils literal notranslate">IMAP4.enable()</code></a>
method. A new <a class="reference internal" href="../library/imaplib.html#imaplib.IMAP4.utf8_enabled" title="imaplib.IMAP4.utf8_enabled"><code class="xref py py-attr docutils literal notranslate">IMAP4.utf8_enabled</code></a>
attribute tracks whether or not <a class="rfc reference external" href="https://tools.ietf.org/html/rfc6855.html">RFC 6855</a> support is enabled.
(Contributed by Milan Oberkirch, R. David Murray, and Maciej Szulik in
<a class="reference external" href="https://bugs.python.org/issue21800">bpo-21800</a>.)
The <a class="reference internal" href="../library/imaplib.html#module-imaplib" title="imaplib: IMAP4 protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">imaplib</code></a> module now automatically encodes non-ASCII string usernames
and passwords using UTF-8, as recommended by the RFCs. (Contributed by Milan
Oberkirch in <a class="reference external" href="https://bugs.python.org/issue21800">bpo-21800</a>.)
</div>
<div class="section" id="imghdr">
<h3>imghdr<a class="headerlink" href="#imghdr" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/imghdr.html#imghdr.what" title="imghdr.what"><code class="xref py py-func docutils literal notranslate">what()</code></a> function now recognizes the
<a class="reference external" href="http://www.openexr.com">OpenEXR</a> format
(contributed by Martin Vignali and Claudiu Popa in <a class="reference external" href="https://bugs.python.org/issue20295">bpo-20295</a>),
and the <a class="reference external" href="https://en.wikipedia.org/wiki/WebP">WebP</a> format
(contributed by Fabrice Aneche and Claudiu Popa in <a class="reference external" href="https://bugs.python.org/issue20197">bpo-20197</a>.)
</div>
<div class="section" id="importlib">
<h3>importlib<a class="headerlink" href="#importlib" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/importlib.html#importlib.util.LazyLoader" title="importlib.util.LazyLoader"><code class="xref py py-class docutils literal notranslate">util.LazyLoader</code></a> class allows for
lazy loading of modules in applications where startup time is important.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue17621">bpo-17621</a>.)
The <a class="reference internal" href="../library/importlib.html#importlib.abc.InspectLoader.source_to_code" title="importlib.abc.InspectLoader.source_to_code"><code class="xref py py-func docutils literal notranslate">abc.InspectLoader.source_to_code()</code></a>
method is now a static method. This makes it easier to initialize a module
object with code compiled from a string by running
<code class="docutils literal notranslate">exec(code, module.__dict__)</code>.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue21156">bpo-21156</a>.)
The new <a class="reference internal" href="../library/importlib.html#importlib.util.module_from_spec" title="importlib.util.module_from_spec"><code class="xref py py-func docutils literal notranslate">util.module_from_spec()</code></a>
function is now the preferred way to create a new module. As opposed to
creating a <a class="reference internal" href="../library/types.html#types.ModuleType" title="types.ModuleType"><code class="xref py py-class docutils literal notranslate">types.ModuleType</code></a> instance directly, this new function
will set the various import-controlled attributes based on the passed-in
spec object. (Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue20383">bpo-20383</a>.)
</div>
<div class="section" id="inspect">
<h3>inspect<a class="headerlink" href="#inspect" title="Permalink to this headline">¶</a></h3>
Both the <a class="reference internal" href="../library/inspect.html#inspect.Signature" title="inspect.Signature"><code class="xref py py-class docutils literal notranslate">Signature</code></a> and <a class="reference internal" href="../library/inspect.html#inspect.Parameter" title="inspect.Parameter"><code class="xref py py-class docutils literal notranslate">Parameter</code></a> classes are
now picklable and hashable. (Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue20726">bpo-20726</a>
and <a class="reference external" href="https://bugs.python.org/issue20334">bpo-20334</a>.)
A new
<a class="reference internal" href="../library/inspect.html#inspect.BoundArguments.apply_defaults" title="inspect.BoundArguments.apply_defaults"><code class="xref py py-meth docutils literal notranslate">BoundArguments.apply_defaults()</code></a>
method provides a way to set default values for missing arguments:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; def foo(a, b=&#39;ham&#39;, *args): pass
&gt;&gt;&gt; ba = inspect.signature(foo).bind(&#39;spam&#39;)
&gt;&gt;&gt; ba.apply_defaults()
&gt;&gt;&gt; ba.arguments
OrderedDict([(&#39;a&#39;, &#39;spam&#39;), (&#39;b&#39;, &#39;ham&#39;), (&#39;args&#39;, ())])
</pre></div>
</div>
(Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue24190">bpo-24190</a>.)
A new class method
<a class="reference internal" href="../library/inspect.html#inspect.Signature.from_callable" title="inspect.Signature.from_callable"><code class="xref py py-meth docutils literal notranslate">Signature.from_callable()</code></a> makes
subclassing of <a class="reference internal" href="../library/inspect.html#inspect.Signature" title="inspect.Signature"><code class="xref py py-class docutils literal notranslate">Signature</code></a> easier. (Contributed
by Yury Selivanov and Eric Snow in <a class="reference external" href="https://bugs.python.org/issue17373">bpo-17373</a>.)
The <a class="reference internal" href="../library/inspect.html#inspect.signature" title="inspect.signature"><code class="xref py py-func docutils literal notranslate">signature()</code></a> function now accepts a follow_wrapped
optional keyword argument, which, when set to <code class="docutils literal notranslate">False</code>, disables automatic
following of <code class="docutils literal notranslate">__wrapped__</code> links.
(Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue20691">bpo-20691</a>.)
A set of new functions to inspect
<a class="reference internal" href="../glossary.html#term-coroutine-function">coroutine functions</a> and
<a class="reference internal" href="../glossary.html#term-coroutine">coroutine objects</a> has been added:
<a class="reference internal" href="../library/inspect.html#inspect.iscoroutine" title="inspect.iscoroutine"><code class="xref py py-func docutils literal notranslate">iscoroutine()</code></a>, <a class="reference internal" href="../library/inspect.html#inspect.iscoroutinefunction" title="inspect.iscoroutinefunction"><code class="xref py py-func docutils literal notranslate">iscoroutinefunction()</code></a>,
<a class="reference internal" href="../library/inspect.html#inspect.isawaitable" title="inspect.isawaitable"><code class="xref py py-func docutils literal notranslate">isawaitable()</code></a>, <a class="reference internal" href="../library/inspect.html#inspect.getcoroutinelocals" title="inspect.getcoroutinelocals"><code class="xref py py-func docutils literal notranslate">getcoroutinelocals()</code></a>,
and <a class="reference internal" href="../library/inspect.html#inspect.getcoroutinestate" title="inspect.getcoroutinestate"><code class="xref py py-func docutils literal notranslate">getcoroutinestate()</code></a>.
(Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue24017">bpo-24017</a> and <a class="reference external" href="https://bugs.python.org/issue24400">bpo-24400</a>.)
The <a class="reference internal" href="../library/inspect.html#inspect.stack" title="inspect.stack"><code class="xref py py-func docutils literal notranslate">stack()</code></a>, <a class="reference internal" href="../library/inspect.html#inspect.trace" title="inspect.trace"><code class="xref py py-func docutils literal notranslate">trace()</code></a>,
<a class="reference internal" href="../library/inspect.html#inspect.getouterframes" title="inspect.getouterframes"><code class="xref py py-func docutils literal notranslate">getouterframes()</code></a>, and <a class="reference internal" href="../library/inspect.html#inspect.getinnerframes" title="inspect.getinnerframes"><code class="xref py py-func docutils literal notranslate">getinnerframes()</code></a>
functions now return a list of named tuples.
(Contributed by Daniel Shahaf in <a class="reference external" href="https://bugs.python.org/issue16808">bpo-16808</a>.)
</div>
<div class="section" id="io">
<h3>io<a class="headerlink" href="#io" title="Permalink to this headline">¶</a></h3>
A new <a class="reference internal" href="../library/io.html#io.BufferedIOBase.readinto1" title="io.BufferedIOBase.readinto1"><code class="xref py py-meth docutils literal notranslate">BufferedIOBase.readinto1()</code></a>
method, that uses at most one call to the underlying raw stream’s
<a class="reference internal" href="../library/io.html#io.RawIOBase.read" title="io.RawIOBase.read"><code class="xref py py-meth docutils literal notranslate">RawIOBase.read()</code></a> or
<a class="reference internal" href="../library/io.html#io.RawIOBase.readinto" title="io.RawIOBase.readinto"><code class="xref py py-meth docutils literal notranslate">RawIOBase.readinto()</code></a> methods.
(Contributed by Nikolaus Rath in <a class="reference external" href="https://bugs.python.org/issue20578">bpo-20578</a>.)
</div>
<div class="section" id="ipaddress">
<h3>ipaddress<a class="headerlink" href="#ipaddress" title="Permalink to this headline">¶</a></h3>
Both the <a class="reference internal" href="../library/ipaddress.html#ipaddress.IPv4Network" title="ipaddress.IPv4Network"><code class="xref py py-class docutils literal notranslate">IPv4Network</code></a> and <a class="reference internal" href="../library/ipaddress.html#ipaddress.IPv6Network" title="ipaddress.IPv6Network"><code class="xref py py-class docutils literal notranslate">IPv6Network</code></a> classes
now accept an <code class="docutils literal notranslate">(address, netmask)</code> tuple argument, so as to easily construct
network objects from existing addresses:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import ipaddress
&gt;&gt;&gt; ipaddress.IPv4Network((&#39;127.0.0.0&#39;, 8))
IPv4Network(&#39;127.0.0.0/8&#39;)
&gt;&gt;&gt; ipaddress.IPv4Network((&#39;127.0.0.0&#39;, &#39;255.0.0.0&#39;))
IPv4Network(&#39;127.0.0.0/8&#39;)
</pre></div>
</div>
(Contributed by Peter Moody and Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue16531">bpo-16531</a>.)
A new <code class="xref py py-attr docutils literal notranslate">reverse_pointer</code> attribute for the
<a class="reference internal" href="../library/ipaddress.html#ipaddress.IPv4Network" title="ipaddress.IPv4Network"><code class="xref py py-class docutils literal notranslate">IPv4Network</code></a> and <a class="reference internal" href="../library/ipaddress.html#ipaddress.IPv6Network" title="ipaddress.IPv6Network"><code class="xref py py-class docutils literal notranslate">IPv6Network</code></a> classes
returns the name of the reverse DNS PTR record:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import ipaddress
&gt;&gt;&gt; addr = ipaddress.IPv4Address(&#39;127.0.0.1&#39;)
&gt;&gt;&gt; addr.reverse_pointer
&#39;1.0.0.127.in-addr.arpa&#39;
&gt;&gt;&gt; addr6 = ipaddress.IPv6Address(&#39;::1&#39;)
&gt;&gt;&gt; addr6.reverse_pointer
&#39;1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa&#39;
</pre></div>
</div>
(Contributed by Leon Weber in <a class="reference external" href="https://bugs.python.org/issue20480">bpo-20480</a>.)
</div>
<div class="section" id="json">
<h3>json<a class="headerlink" href="#json" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/json.html#module-json.tool" title="json.tool: A command line to validate and pretty-print JSON."><code class="xref py py-mod docutils literal notranslate">json.tool</code></a> command line interface now preserves the order of keys in
JSON objects passed in input. The new <code class="docutils literal notranslate">--sort-keys</code> option can be used
to sort the keys alphabetically. (Contributed by Berker Peksag
in <a class="reference external" href="https://bugs.python.org/issue21650">bpo-21650</a>.)
JSON decoder now raises <a class="reference internal" href="../library/json.html#json.JSONDecodeError" title="json.JSONDecodeError"><code class="xref py py-exc docutils literal notranslate">JSONDecodeError</code></a> instead of
<a class="reference internal" href="../library/exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> to provide better context information about the error.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue19361">bpo-19361</a>.)
</div>
<div class="section" id="linecache">
<h3>linecache<a class="headerlink" href="#linecache" title="Permalink to this headline">¶</a></h3>
A new <a class="reference internal" href="../library/linecache.html#linecache.lazycache" title="linecache.lazycache"><code class="xref py py-func docutils literal notranslate">lazycache()</code></a> function can be used to capture information
about a non-file-based module to permit getting its lines later via
<a class="reference internal" href="../library/linecache.html#linecache.getline" title="linecache.getline"><code class="xref py py-func docutils literal notranslate">getline()</code></a>. This avoids doing I/O until a line is actually
needed, without having to carry the module globals around indefinitely.
(Contributed by Robert Collins in <a class="reference external" href="https://bugs.python.org/issue17911">bpo-17911</a>.)
</div>
<div class="section" id="locale">
<h3>locale<a class="headerlink" href="#locale" title="Permalink to this headline">¶</a></h3>
A new <a class="reference internal" href="../library/locale.html#locale.delocalize" title="locale.delocalize"><code class="xref py py-func docutils literal notranslate">delocalize()</code></a> function can be used to convert a string into
a normalized number string, taking the <code class="docutils literal notranslate">LC_NUMERIC</code> settings into account:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import locale
&gt;&gt;&gt; locale.setlocale(locale.LC_NUMERIC, &#39;de_DE.UTF-8&#39;)
&#39;de_DE.UTF-8&#39;
&gt;&gt;&gt; locale.delocalize(&#39;1.234,56&#39;)
&#39;1234.56&#39;
&gt;&gt;&gt; locale.setlocale(locale.LC_NUMERIC, &#39;en_US.UTF-8&#39;)
&#39;en_US.UTF-8&#39;
&gt;&gt;&gt; locale.delocalize(&#39;1,234.56&#39;)
&#39;1234.56&#39;
</pre></div>
</div>
(Contributed by Cédric Krier in <a class="reference external" href="https://bugs.python.org/issue13918">bpo-13918</a>.)
</div>
<div class="section" id="logging">
<h3>logging<a class="headerlink" href="#logging" title="Permalink to this headline">¶</a></h3>
All logging methods (<a class="reference internal" href="../library/logging.html#logging.Logger" title="logging.Logger"><code class="xref py py-class docutils literal notranslate">Logger</code></a> <a class="reference internal" href="../library/logging.html#logging.Logger.log" title="logging.Logger.log"><code class="xref py py-meth docutils literal notranslate">log()</code></a>,
<a class="reference internal" href="../library/logging.html#logging.Logger.exception" title="logging.Logger.exception"><code class="xref py py-meth docutils literal notranslate">exception()</code></a>, <a class="reference internal" href="../library/logging.html#logging.Logger.critical" title="logging.Logger.critical"><code class="xref py py-meth docutils literal notranslate">critical()</code></a>,
<a class="reference internal" href="../library/logging.html#logging.Logger.debug" title="logging.Logger.debug"><code class="xref py py-meth docutils literal notranslate">debug()</code></a>, etc.), now accept exception instances
as an exc_info argument, in addition to boolean values and exception
tuples:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import logging
&gt;&gt;&gt; try:
... 1/0
... except ZeroDivisionError as ex:
... logging.error(&#39;exception&#39;, exc_info=ex)
ERROR:root:exception
</pre></div>
</div>
(Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue20537">bpo-20537</a>.)
The <a class="reference internal" href="../library/logging.handlers.html#logging.handlers.HTTPHandler" title="logging.handlers.HTTPHandler"><code class="xref py py-class docutils literal notranslate">handlers.HTTPHandler</code></a> class now
accepts an optional <a class="reference internal" href="../library/ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate">ssl.SSLContext</code></a> instance to configure SSL
settings used in an HTTP connection.
(Contributed by Alex Gaynor in <a class="reference external" href="https://bugs.python.org/issue22788">bpo-22788</a>.)
The <a class="reference internal" href="../library/logging.handlers.html#logging.handlers.QueueListener" title="logging.handlers.QueueListener"><code class="xref py py-class docutils literal notranslate">handlers.QueueListener</code></a> class now
takes a respect_handler_level keyword argument which, if set to <code class="docutils literal notranslate">True</code>,
will pass messages to handlers taking handler levels into account.
(Contributed by Vinay Sajip.)
</div>
<div class="section" id="lzma">
<h3>lzma<a class="headerlink" href="#lzma" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/lzma.html#lzma.LZMADecompressor.decompress" title="lzma.LZMADecompressor.decompress"><code class="xref py py-meth docutils literal notranslate">LZMADecompressor.decompress()</code></a>
method now accepts an optional max_length argument to limit the maximum
size of decompressed data.
(Contributed by Martin Panter in <a class="reference external" href="https://bugs.python.org/issue15955">bpo-15955</a>.)
</div>
<div class="section" id="math">
<h3>math<a class="headerlink" href="#math" title="Permalink to this headline">¶</a></h3>
Two new constants have been added to the <a class="reference internal" href="../library/math.html#module-math" title="math: Mathematical functions (sin() etc.)."><code class="xref py py-mod docutils literal notranslate">math</code></a> module: <a class="reference internal" href="../library/math.html#math.inf" title="math.inf"><code class="xref py py-data docutils literal notranslate">inf</code></a>
and <a class="reference internal" href="../library/math.html#math.nan" title="math.nan"><code class="xref py py-data docutils literal notranslate">nan</code></a>. (Contributed by Mark Dickinson in <a class="reference external" href="https://bugs.python.org/issue23185">bpo-23185</a>.)
A new function <a class="reference internal" href="../library/math.html#math.isclose" title="math.isclose"><code class="xref py py-func docutils literal notranslate">isclose()</code></a> provides a way to test for approximate
equality. (Contributed by Chris Barker and Tal Einat in <a class="reference external" href="https://bugs.python.org/issue24270">bpo-24270</a>.)
A new <a class="reference internal" href="../library/math.html#math.gcd" title="math.gcd"><code class="xref py py-func docutils literal notranslate">gcd()</code></a> function has been added. The <a class="reference internal" href="../library/fractions.html#fractions.gcd" title="fractions.gcd"><code class="xref py py-func docutils literal notranslate">fractions.gcd()</code></a>
function is now deprecated. (Contributed by Mark Dickinson and Serhiy
Storchaka in <a class="reference external" href="https://bugs.python.org/issue22486">bpo-22486</a>.)
</div>
<div class="section" id="multiprocessing">
<h3>multiprocessing<a class="headerlink" href="#multiprocessing" title="Permalink to this headline">¶</a></h3>
<a class="reference internal" href="../library/multiprocessing.html#multiprocessing.sharedctypes.synchronized" title="multiprocessing.sharedctypes.synchronized"><code class="xref py py-func docutils literal notranslate">sharedctypes.synchronized()</code></a>
objects now support the <a class="reference internal" href="../glossary.html#term-context-manager">context manager</a> protocol.
(Contributed by Charles-François Natali in <a class="reference external" href="https://bugs.python.org/issue21565">bpo-21565</a>.)
</div>
<div class="section" id="operator">
<h3>operator<a class="headerlink" href="#operator" title="Permalink to this headline">¶</a></h3>
<a class="reference internal" href="../library/operator.html#operator.attrgetter" title="operator.attrgetter"><code class="xref py py-func docutils literal notranslate">attrgetter()</code></a>, <a class="reference internal" href="../library/operator.html#operator.itemgetter" title="operator.itemgetter"><code class="xref py py-func docutils literal notranslate">itemgetter()</code></a>,
and <a class="reference internal" href="../library/operator.html#operator.methodcaller" title="operator.methodcaller"><code class="xref py py-func docutils literal notranslate">methodcaller()</code></a> objects now support pickling.
(Contributed by Josh Rosenberg and Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue22955">bpo-22955</a>.)
New <a class="reference internal" href="../library/operator.html#operator.matmul" title="operator.matmul"><code class="xref py py-func docutils literal notranslate">matmul()</code></a> and <a class="reference internal" href="../library/operator.html#operator.imatmul" title="operator.imatmul"><code class="xref py py-func docutils literal notranslate">imatmul()</code></a> functions
to perform matrix multiplication.
(Contributed by Benjamin Peterson in <a class="reference external" href="https://bugs.python.org/issue21176">bpo-21176</a>.)
</div>
<div class="section" id="os">
<h3>os<a class="headerlink" href="#os" title="Permalink to this headline">¶</a></h3>
The new <a class="reference internal" href="../library/os.html#os.scandir" title="os.scandir"><code class="xref py py-func docutils literal notranslate">scandir()</code></a> function returning an iterator of
<a class="reference internal" href="../library/os.html#os.DirEntry" title="os.DirEntry"><code class="xref py py-class docutils literal notranslate">DirEntry</code></a> objects has been added. If possible, <a class="reference internal" href="../library/os.html#os.scandir" title="os.scandir"><code class="xref py py-func docutils literal notranslate">scandir()</code></a>
extracts file attributes while scanning a directory, removing the need to
perform subsequent system calls to determine file type or attributes, which may
significantly improve performance. (Contributed by Ben Hoyt with the help
of Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue22524">bpo-22524</a>.)
On Windows, a new
<a class="reference internal" href="../library/os.html#os.stat_result.st_file_attributes" title="os.stat_result.st_file_attributes"><code class="xref py py-attr docutils literal notranslate">stat_result.st_file_attributes</code></a>
attribute is now available. It corresponds to the <code class="docutils literal notranslate">dwFileAttributes</code> member
of the <code class="docutils literal notranslate">BY_HANDLE_FILE_INFORMATION</code> structure returned by
<code class="docutils literal notranslate">GetFileInformationByHandle()</code>. (Contributed by Ben Hoyt in <a class="reference external" href="https://bugs.python.org/issue21719">bpo-21719</a>.)
The <a class="reference internal" href="../library/os.html#os.urandom" title="os.urandom"><code class="xref py py-func docutils literal notranslate">urandom()</code></a> function now uses the <code class="docutils literal notranslate">getrandom()</code> syscall on Linux 3.17
or newer, and <code class="docutils literal notranslate">getentropy()</code> on OpenBSD 5.6 and newer, removing the need to
use <code class="docutils literal notranslate">/dev/urandom</code> and avoiding failures due to potential file descriptor
exhaustion. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue22181">bpo-22181</a>.)
New <a class="reference internal" href="../library/os.html#os.get_blocking" title="os.get_blocking"><code class="xref py py-func docutils literal notranslate">get_blocking()</code></a> and <a class="reference internal" href="../library/os.html#os.set_blocking" title="os.set_blocking"><code class="xref py py-func docutils literal notranslate">set_blocking()</code></a> functions allow
getting and setting a file descriptor’s blocking mode (<a class="reference internal" href="../library/os.html#os.O_NONBLOCK" title="os.O_NONBLOCK"><code class="xref py py-data docutils literal notranslate">O_NONBLOCK</code></a>.)
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue22054">bpo-22054</a>.)
The <a class="reference internal" href="../library/os.html#os.truncate" title="os.truncate"><code class="xref py py-func docutils literal notranslate">truncate()</code></a> and <a class="reference internal" href="../library/os.html#os.ftruncate" title="os.ftruncate"><code class="xref py py-func docutils literal notranslate">ftruncate()</code></a> functions are now supported
on Windows. (Contributed by Steve Dower in <a class="reference external" href="https://bugs.python.org/issue23668">bpo-23668</a>.)
There is a new <a class="reference internal" href="../library/os.path.html#os.path.commonpath" title="os.path.commonpath"><code class="xref py py-func docutils literal notranslate">os.path.commonpath()</code></a> function returning the longest
common sub-path of each passed pathname. Unlike the
<a class="reference internal" href="../library/os.path.html#os.path.commonprefix" title="os.path.commonprefix"><code class="xref py py-func docutils literal notranslate">os.path.commonprefix()</code></a> function, it always returns a valid
path:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; os.path.commonprefix([&#39;/usr/lib&#39;, &#39;/usr/local/lib&#39;])
&#39;/usr/l&#39;

&gt;&gt;&gt; os.path.commonpath([&#39;/usr/lib&#39;, &#39;/usr/local/lib&#39;])
&#39;/usr&#39;
</pre></div>
</div>
(Contributed by Rafik Draoui and Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue10395">bpo-10395</a>.)
</div>
<div class="section" id="pathlib">
<h3>pathlib<a class="headerlink" href="#pathlib" title="Permalink to this headline">¶</a></h3>
The new <a class="reference internal" href="../library/pathlib.html#pathlib.Path.samefile" title="pathlib.Path.samefile"><code class="xref py py-meth docutils literal notranslate">Path.samefile()</code></a> method can be used
to check whether the path points to the same file as another path, which can
be either another <a class="reference internal" href="../library/pathlib.html#pathlib.Path" title="pathlib.Path"><code class="xref py py-class docutils literal notranslate">Path</code></a> object, or a string:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import pathlib
&gt;&gt;&gt; p1 = pathlib.Path(&#39;/etc/hosts&#39;)
&gt;&gt;&gt; p2 = pathlib.Path(&#39;/etc/../etc/hosts&#39;)
&gt;&gt;&gt; p1.samefile(p2)
True
</pre></div>
</div>
(Contributed by Vajrasky Kok and Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue19775">bpo-19775</a>.)
The <a class="reference internal" href="../library/pathlib.html#pathlib.Path.mkdir" title="pathlib.Path.mkdir"><code class="xref py py-meth docutils literal notranslate">Path.mkdir()</code></a> method now accepts a new optional
exist_ok argument to match <code class="docutils literal notranslate">mkdir -p</code> and <a class="reference internal" href="../library/os.html#os.makedirs" title="os.makedirs"><code class="xref py py-func docutils literal notranslate">os.makedirs()</code></a>
functionality. (Contributed by Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue21539">bpo-21539</a>.)
There is a new <a class="reference internal" href="../library/pathlib.html#pathlib.Path.expanduser" title="pathlib.Path.expanduser"><code class="xref py py-meth docutils literal notranslate">Path.expanduser()</code></a> method to
expand <code class="docutils literal notranslate">~</code> and <code class="docutils literal notranslate">~user</code> prefixes. (Contributed by Serhiy Storchaka and
Claudiu Popa in <a class="reference external" href="https://bugs.python.org/issue19776">bpo-19776</a>.)
A new <a class="reference internal" href="../library/pathlib.html#pathlib.Path.home" title="pathlib.Path.home"><code class="xref py py-meth docutils literal notranslate">Path.home()</code></a> class method can be used to get
a <a class="reference internal" href="../library/pathlib.html#pathlib.Path" title="pathlib.Path"><code class="xref py py-class docutils literal notranslate">Path</code></a> instance representing the user’s home
directory.
(Contributed by Victor Salgado and Mayank Tripathi in <a class="reference external" href="https://bugs.python.org/issue19777">bpo-19777</a>.)
New <a class="reference internal" href="../library/pathlib.html#pathlib.Path.write_text" title="pathlib.Path.write_text"><code class="xref py py-meth docutils literal notranslate">Path.write_text()</code></a>,
<a class="reference internal" href="../library/pathlib.html#pathlib.Path.read_text" title="pathlib.Path.read_text"><code class="xref py py-meth docutils literal notranslate">Path.read_text()</code></a>,
<a class="reference internal" href="../library/pathlib.html#pathlib.Path.write_bytes" title="pathlib.Path.write_bytes"><code class="xref py py-meth docutils literal notranslate">Path.write_bytes()</code></a>,
<a class="reference internal" href="../library/pathlib.html#pathlib.Path.read_bytes" title="pathlib.Path.read_bytes"><code class="xref py py-meth docutils literal notranslate">Path.read_bytes()</code></a> methods to simplify
read/write operations on files.
The following code snippet will create or rewrite existing file
<code class="docutils literal notranslate">~/spam42</code>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import pathlib
&gt;&gt;&gt; p = pathlib.Path(&#39;~/spam42&#39;)
&gt;&gt;&gt; p.expanduser().write_text(&#39;ham&#39;)
3
</pre></div>
</div>
(Contributed by Christopher Welborn in <a class="reference external" href="https://bugs.python.org/issue20218">bpo-20218</a>.)
</div>
<div class="section" id="pickle">
<h3>pickle<a class="headerlink" href="#pickle" title="Permalink to this headline">¶</a></h3>
Nested objects, such as unbound methods or nested classes, can now be pickled
using <a class="reference internal" href="../library/pickle.html#pickle-protocols">pickle protocols</a> older than protocol version 4.
Protocol version 4 already supports these cases. (Contributed by Serhiy
Storchaka in <a class="reference external" href="https://bugs.python.org/issue23611">bpo-23611</a>.)
</div>
<div class="section" id="poplib">
<h3>poplib<a class="headerlink" href="#poplib" title="Permalink to this headline">¶</a></h3>
A new <a class="reference internal" href="../library/poplib.html#poplib.POP3.utf8" title="poplib.POP3.utf8"><code class="xref py py-meth docutils literal notranslate">POP3.utf8()</code></a> command enables <a class="rfc reference external" href="https://tools.ietf.org/html/rfc6856.html">RFC 6856</a>
(Internationalized Email) support, if a POP server supports it.
(Contributed by Milan OberKirch in <a class="reference external" href="https://bugs.python.org/issue21804">bpo-21804</a>.)
</div>
<div class="section" id="re">
<h3>re<a class="headerlink" href="#re" title="Permalink to this headline">¶</a></h3>
References and conditional references to groups with fixed length are now
allowed in lookbehind assertions:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import re
&gt;&gt;&gt; pat = re.compile(r&#39;(a|b).(?&lt;=\1)c&#39;)
&gt;&gt;&gt; pat.match(&#39;aac&#39;)
&lt;_sre.SRE_Match object; span=(0, 3), match=&#39;aac&#39;&gt;
&gt;&gt;&gt; pat.match(&#39;bbc&#39;)
&lt;_sre.SRE_Match object; span=(0, 3), match=&#39;bbc&#39;&gt;
</pre></div>
</div>
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue9179">bpo-9179</a>.)
The number of capturing groups in regular expressions is no longer limited to
100. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue22437">bpo-22437</a>.)
The <a class="reference internal" href="../library/re.html#re.sub" title="re.sub"><code class="xref py py-func docutils literal notranslate">sub()</code></a> and <a class="reference internal" href="../library/re.html#re.subn" title="re.subn"><code class="xref py py-func docutils literal notranslate">subn()</code></a> functions now replace unmatched
groups with empty strings instead of raising an exception.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue1519638">bpo-1519638</a>.)
The <a class="reference internal" href="../library/re.html#re.error" title="re.error"><code class="xref py py-class docutils literal notranslate">re.error</code></a> exceptions have new attributes,
<a class="reference internal" href="../library/re.html#re.error.msg" title="re.error.msg"><code class="xref py py-attr docutils literal notranslate">msg</code></a>, <a class="reference internal" href="../library/re.html#re.error.pattern" title="re.error.pattern"><code class="xref py py-attr docutils literal notranslate">pattern</code></a>,
<a class="reference internal" href="../library/re.html#re.error.pos" title="re.error.pos"><code class="xref py py-attr docutils literal notranslate">pos</code></a>, <a class="reference internal" href="../library/re.html#re.error.lineno" title="re.error.lineno"><code class="xref py py-attr docutils literal notranslate">lineno</code></a>,
and <a class="reference internal" href="../library/re.html#re.error.colno" title="re.error.colno"><code class="xref py py-attr docutils literal notranslate">colno</code></a>, that provide better context
information about the error:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; re.compile(&quot;&quot;&quot;
... (?x)
... .++
... &quot;&quot;&quot;)
Traceback (most recent call last):
 ...
sre_constants.error: multiple repeat at position 16 (line 3, column 7)
</pre></div>
</div>
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue22578">bpo-22578</a>.)
</div>
<div class="section" id="readline">
<h3>readline<a class="headerlink" href="#readline" title="Permalink to this headline">¶</a></h3>
A new <a class="reference internal" href="../library/readline.html#readline.append_history_file" title="readline.append_history_file"><code class="xref py py-func docutils literal notranslate">append_history_file()</code></a> function can be used to append
the specified number of trailing elements in history to the given file.
(Contributed by Bruno Cauet in <a class="reference external" href="https://bugs.python.org/issue22940">bpo-22940</a>.)
</div>
<div class="section" id="selectors">
<h3>selectors<a class="headerlink" href="#selectors" title="Permalink to this headline">¶</a></h3>
The new <a class="reference internal" href="../library/selectors.html#selectors.DevpollSelector" title="selectors.DevpollSelector"><code class="xref py py-class docutils literal notranslate">DevpollSelector</code></a> supports efficient
<code class="docutils literal notranslate">/dev/poll</code> polling on Solaris.
(Contributed by Giampaolo Rodola’ in <a class="reference external" href="https://bugs.python.org/issue18931">bpo-18931</a>.)
</div>
<div class="section" id="shutil">
<h3>shutil<a class="headerlink" href="#shutil" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/shutil.html#shutil.move" title="shutil.move"><code class="xref py py-func docutils literal notranslate">move()</code></a> function now accepts a copy_function argument,
allowing, for example, the <a class="reference internal" href="../library/shutil.html#shutil.copy" title="shutil.copy"><code class="xref py py-func docutils literal notranslate">copy()</code></a> function to be used instead of
the default <a class="reference internal" href="../library/shutil.html#shutil.copy2" title="shutil.copy2"><code class="xref py py-func docutils literal notranslate">copy2()</code></a> if there is a need to ignore file metadata
when moving.
(Contributed by Claudiu Popa in <a class="reference external" href="https://bugs.python.org/issue19840">bpo-19840</a>.)
The <a class="reference internal" href="../library/shutil.html#shutil.make_archive" title="shutil.make_archive"><code class="xref py py-func docutils literal notranslate">make_archive()</code></a> function now supports the xztar format.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue5411">bpo-5411</a>.)
</div>
<div class="section" id="signal">
<h3>signal<a class="headerlink" href="#signal" title="Permalink to this headline">¶</a></h3>
On Windows, the <a class="reference internal" href="../library/signal.html#signal.set_wakeup_fd" title="signal.set_wakeup_fd"><code class="xref py py-func docutils literal notranslate">set_wakeup_fd()</code></a> function now also supports
socket handles. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue22018">bpo-22018</a>.)
Various <code class="docutils literal notranslate">SIG*</code> constants in the <a class="reference internal" href="../library/signal.html#module-signal" title="signal: Set handlers for asynchronous events."><code class="xref py py-mod docutils literal notranslate">signal</code></a> module have been converted into
<a class="reference internal" href="../library/enum.html#module-enum" title="enum: Implementation of an enumeration class."><code class="xref py py-mod docutils literal notranslate">Enums</code></a>. This allows meaningful names to be printed
during debugging, instead of integer “magic numbers”.
(Contributed by Giampaolo Rodola’ in <a class="reference external" href="https://bugs.python.org/issue21076">bpo-21076</a>.)
</div>
<div class="section" id="smtpd">
<h3>smtpd<a class="headerlink" href="#smtpd" title="Permalink to this headline">¶</a></h3>
Both the <a class="reference internal" href="../library/smtpd.html#smtpd.SMTPServer" title="smtpd.SMTPServer"><code class="xref py py-class docutils literal notranslate">SMTPServer</code></a> and <a class="reference internal" href="../library/smtpd.html#smtpd.SMTPChannel" title="smtpd.SMTPChannel"><code class="xref py py-class docutils literal notranslate">SMTPChannel</code></a> classes now
accept a decode_data keyword argument to determine if the <code class="docutils literal notranslate">DATA</code> portion of
the SMTP transaction is decoded using the <code class="docutils literal notranslate">&quot;utf-8&quot;</code> codec or is instead
provided to the
<a class="reference internal" href="../library/smtpd.html#smtpd.SMTPServer.process_message" title="smtpd.SMTPServer.process_message"><code class="xref py py-meth docutils literal notranslate">SMTPServer.process_message()</code></a>
method as a byte string. The default is <code class="docutils literal notranslate">True</code> for backward compatibility
reasons, but will change to <code class="docutils literal notranslate">False</code> in Python 3.6. If decode_data is set
to <code class="docutils literal notranslate">False</code>, the <code class="docutils literal notranslate">process_message</code> method must be prepared to accept keyword
arguments.
(Contributed by Maciej Szulik in <a class="reference external" href="https://bugs.python.org/issue19662">bpo-19662</a>.)
The <a class="reference internal" href="../library/smtpd.html#smtpd.SMTPServer" title="smtpd.SMTPServer"><code class="xref py py-class docutils literal notranslate">SMTPServer</code></a> class now advertises the <code class="docutils literal notranslate">8BITMIME</code> extension
(<a class="rfc reference external" href="https://tools.ietf.org/html/rfc6152.html">RFC 6152</a>) if decode_data has been set <code class="docutils literal notranslate">True</code>. If the client
specifies <code class="docutils literal notranslate">BODY=8BITMIME</code> on the <code class="docutils literal notranslate">MAIL</code> command, it is passed to
<a class="reference internal" href="../library/smtpd.html#smtpd.SMTPServer.process_message" title="smtpd.SMTPServer.process_message"><code class="xref py py-meth docutils literal notranslate">SMTPServer.process_message()</code></a>
via the mail_options keyword.
(Contributed by Milan Oberkirch and R. David Murray in <a class="reference external" href="https://bugs.python.org/issue21795">bpo-21795</a>.)
The <a class="reference internal" href="../library/smtpd.html#smtpd.SMTPServer" title="smtpd.SMTPServer"><code class="xref py py-class docutils literal notranslate">SMTPServer</code></a> class now also supports the <code class="docutils literal notranslate">SMTPUTF8</code>
extension (<a class="rfc reference external" href="https://tools.ietf.org/html/rfc6531.html">RFC 6531</a>: Internationalized Email). If the client specified
<code class="docutils literal notranslate">SMTPUTF8 BODY=8BITMIME</code> on the <code class="docutils literal notranslate">MAIL</code> command, they are passed to
<a class="reference internal" href="../library/smtpd.html#smtpd.SMTPServer.process_message" title="smtpd.SMTPServer.process_message"><code class="xref py py-meth docutils literal notranslate">SMTPServer.process_message()</code></a>
via the mail_options keyword. It is the responsibility of the
<code class="docutils literal notranslate">process_message</code> method to correctly handle the <code class="docutils literal notranslate">SMTPUTF8</code> data.
(Contributed by Milan Oberkirch in <a class="reference external" href="https://bugs.python.org/issue21725">bpo-21725</a>.)
It is now possible to provide, directly or via name resolution, IPv6
addresses in the <a class="reference internal" href="../library/smtpd.html#smtpd.SMTPServer" title="smtpd.SMTPServer"><code class="xref py py-class docutils literal notranslate">SMTPServer</code></a> constructor, and have it
successfully connect. (Contributed by Milan Oberkirch in <a class="reference external" href="https://bugs.python.org/issue14758">bpo-14758</a>.)
</div>
<div class="section" id="smtplib">
<h3>smtplib<a class="headerlink" href="#smtplib" title="Permalink to this headline">¶</a></h3>
A new <a class="reference internal" href="../library/smtplib.html#smtplib.SMTP.auth" title="smtplib.SMTP.auth"><code class="xref py py-meth docutils literal notranslate">SMTP.auth()</code></a> method provides a convenient way to
implement custom authentication mechanisms. (Contributed by Milan
Oberkirch in <a class="reference external" href="https://bugs.python.org/issue15014">bpo-15014</a>.)
The <a class="reference internal" href="../library/smtplib.html#smtplib.SMTP.set_debuglevel" title="smtplib.SMTP.set_debuglevel"><code class="xref py py-meth docutils literal notranslate">SMTP.set_debuglevel()</code></a> method now
accepts an additional debuglevel (2), which enables timestamps in debug
messages. (Contributed by Gavin Chappell and Maciej Szulik in <a class="reference external" href="https://bugs.python.org/issue16914">bpo-16914</a>.)
Both the <a class="reference internal" href="../library/smtplib.html#smtplib.SMTP.sendmail" title="smtplib.SMTP.sendmail"><code class="xref py py-meth docutils literal notranslate">SMTP.sendmail()</code></a> and
<a class="reference internal" href="../library/smtplib.html#smtplib.SMTP.send_message" title="smtplib.SMTP.send_message"><code class="xref py py-meth docutils literal notranslate">SMTP.send_message()</code></a> methods now
support <a class="rfc reference external" href="https://tools.ietf.org/html/rfc6531.html">RFC 6531</a> (SMTPUTF8).
(Contributed by Milan Oberkirch and R. David Murray in <a class="reference external" href="https://bugs.python.org/issue22027">bpo-22027</a>.)
</div>
<div class="section" id="sndhdr">
<h3>sndhdr<a class="headerlink" href="#sndhdr" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/sndhdr.html#sndhdr.what" title="sndhdr.what"><code class="xref py py-func docutils literal notranslate">what()</code></a> and <a class="reference internal" href="../library/sndhdr.html#sndhdr.whathdr" title="sndhdr.whathdr"><code class="xref py py-func docutils literal notranslate">whathdr()</code></a> functions now return
a <a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate">namedtuple()</code></a>. (Contributed by Claudiu Popa in
<a class="reference external" href="https://bugs.python.org/issue18615">bpo-18615</a>.)
</div>
<div class="section" id="socket">
<h3>socket<a class="headerlink" href="#socket" title="Permalink to this headline">¶</a></h3>
Functions with timeouts now use a monotonic clock, instead of a system clock.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue22043">bpo-22043</a>.)
A new <a class="reference internal" href="../library/socket.html#socket.socket.sendfile" title="socket.socket.sendfile"><code class="xref py py-meth docutils literal notranslate">socket.sendfile()</code></a> method allows
sending a file over a socket by using the high-performance <a class="reference internal" href="../library/os.html#os.sendfile" title="os.sendfile"><code class="xref py py-func docutils literal notranslate">os.sendfile()</code></a>
function on UNIX, resulting in uploads being from 2 to 3 times faster than when
using plain <a class="reference internal" href="../library/socket.html#socket.socket.send" title="socket.socket.send"><code class="xref py py-meth docutils literal notranslate">socket.send()</code></a>.
(Contributed by Giampaolo Rodola’ in <a class="reference external" href="https://bugs.python.org/issue17552">bpo-17552</a>.)
The <a class="reference internal" href="../library/socket.html#socket.socket.sendall" title="socket.socket.sendall"><code class="xref py py-meth docutils literal notranslate">socket.sendall()</code></a> method no longer resets the
socket timeout every time bytes are received or sent. The socket timeout is
now the maximum total duration to send all data.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue23853">bpo-23853</a>.)
The backlog argument of the <a class="reference internal" href="../library/socket.html#socket.socket.listen" title="socket.socket.listen"><code class="xref py py-meth docutils literal notranslate">socket.listen()</code></a>
method is now optional. By default it is set to
<a class="reference internal" href="../library/socket.html#socket.SOMAXCONN" title="socket.SOMAXCONN"><code class="xref py py-data docutils literal notranslate">SOMAXCONN</code></a> or to <code class="docutils literal notranslate">128</code>, whichever is less.
(Contributed by Charles-François Natali in <a class="reference external" href="https://bugs.python.org/issue21455">bpo-21455</a>.)
</div>
<div class="section" id="ssl">
<h3>ssl<a class="headerlink" href="#ssl" title="Permalink to this headline">¶</a></h3>
<div class="section" id="memory-bio-support">
<h4>Memory BIO Support<a class="headerlink" href="#memory-bio-support" title="Permalink to this headline">¶</a></h4>
(Contributed by Geert Jansen in <a class="reference external" href="https://bugs.python.org/issue21965">bpo-21965</a>.)
The new <a class="reference internal" href="../library/ssl.html#ssl.SSLObject" title="ssl.SSLObject"><code class="xref py py-class docutils literal notranslate">SSLObject</code></a> class has been added to provide SSL protocol
support for cases when the network I/O capabilities of <a class="reference internal" href="../library/ssl.html#ssl.SSLSocket" title="ssl.SSLSocket"><code class="xref py py-class docutils literal notranslate">SSLSocket</code></a>
are not necessary or are suboptimal. <code class="docutils literal notranslate">SSLObject</code> represents
an SSL protocol instance, but does not implement any network I/O methods, and
instead provides a memory buffer interface. The new <a class="reference internal" href="../library/ssl.html#ssl.MemoryBIO" title="ssl.MemoryBIO"><code class="xref py py-class docutils literal notranslate">MemoryBIO</code></a>
class can be used to pass data between Python and an SSL protocol instance.
The memory BIO SSL support is primarily intended to be used in frameworks
implementing asynchronous I/O for which <a class="reference internal" href="../library/ssl.html#ssl.SSLSocket" title="ssl.SSLSocket"><code class="xref py py-class docutils literal notranslate">SSLSocket</code></a>’s readiness
model (“select/poll”) is inefficient.
A new <a class="reference internal" href="../library/ssl.html#ssl.SSLContext.wrap_bio" title="ssl.SSLContext.wrap_bio"><code class="xref py py-meth docutils literal notranslate">SSLContext.wrap_bio()</code></a> method can be used
to create a new <code class="docutils literal notranslate">SSLObject</code> instance.
</div>
<div class="section" id="application-layer-protocol-negotiation-support">
<h4>Application-Layer Protocol Negotiation Support<a class="headerlink" href="#application-layer-protocol-negotiation-support" title="Permalink to this headline">¶</a></h4>
(Contributed by Benjamin Peterson in <a class="reference external" href="https://bugs.python.org/issue20188">bpo-20188</a>.)
Where OpenSSL support is present, the <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate">ssl</code></a> module now implements
the Application-Layer Protocol Negotiation TLS extension as described
in <a class="rfc reference external" href="https://tools.ietf.org/html/rfc7301.html">RFC 7301</a>.
The new <a class="reference internal" href="../library/ssl.html#ssl.SSLContext.set_alpn_protocols" title="ssl.SSLContext.set_alpn_protocols"><code class="xref py py-meth docutils literal notranslate">SSLContext.set_alpn_protocols()</code></a>
can be used to specify which protocols a socket should advertise during
the TLS handshake.
The new
<a class="reference internal" href="../library/ssl.html#ssl.SSLSocket.selected_alpn_protocol" title="ssl.SSLSocket.selected_alpn_protocol"><code class="xref py py-meth docutils literal notranslate">SSLSocket.selected_alpn_protocol()</code></a>
returns the protocol that was selected during the TLS handshake.
The <a class="reference internal" href="../library/ssl.html#ssl.HAS_ALPN" title="ssl.HAS_ALPN"><code class="xref py py-data docutils literal notranslate">HAS_ALPN</code></a> flag indicates whether ALPN support is present.
</div>
<div class="section" id="other-changes">
<h4>Other Changes<a class="headerlink" href="#other-changes" title="Permalink to this headline">¶</a></h4>
There is a new <a class="reference internal" href="../library/ssl.html#ssl.SSLSocket.version" title="ssl.SSLSocket.version"><code class="xref py py-meth docutils literal notranslate">SSLSocket.version()</code></a> method to
query the actual protocol version in use.
(Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue20421">bpo-20421</a>.)
The <a class="reference internal" href="../library/ssl.html#ssl.SSLSocket" title="ssl.SSLSocket"><code class="xref py py-class docutils literal notranslate">SSLSocket</code></a> class now implements
a <code class="xref py py-meth docutils literal notranslate">SSLSocket.sendfile()</code> method.
(Contributed by Giampaolo Rodola’ in <a class="reference external" href="https://bugs.python.org/issue17552">bpo-17552</a>.)
The <code class="xref py py-meth docutils literal notranslate">SSLSocket.send()</code> method now raises either
the <a class="reference internal" href="../library/ssl.html#ssl.SSLWantReadError" title="ssl.SSLWantReadError"><code class="xref py py-exc docutils literal notranslate">ssl.SSLWantReadError</code></a> or <a class="reference internal" href="../library/ssl.html#ssl.SSLWantWriteError" title="ssl.SSLWantWriteError"><code class="xref py py-exc docutils literal notranslate">ssl.SSLWantWriteError</code></a> exception on a
non-blocking socket if the operation would block. Previously, it would return
<code class="docutils literal notranslate">0</code>. (Contributed by Nikolaus Rath in <a class="reference external" href="https://bugs.python.org/issue20951">bpo-20951</a>.)
The <a class="reference internal" href="../library/ssl.html#ssl.cert_time_to_seconds" title="ssl.cert_time_to_seconds"><code class="xref py py-func docutils literal notranslate">cert_time_to_seconds()</code></a> function now interprets the input time
as UTC and not as local time, per <a class="rfc reference external" href="https://tools.ietf.org/html/rfc5280.html">RFC 5280</a>. Additionally, the return
value is always an <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>. (Contributed by Akira Li in <a class="reference external" href="https://bugs.python.org/issue19940">bpo-19940</a>.)
New <code class="xref py py-meth docutils literal notranslate">SSLObject.shared_ciphers()</code> and
<a class="reference internal" href="../library/ssl.html#ssl.SSLSocket.shared_ciphers" title="ssl.SSLSocket.shared_ciphers"><code class="xref py py-meth docutils literal notranslate">SSLSocket.shared_ciphers()</code></a> methods return
the list of ciphers sent by the client during the handshake.
(Contributed by Benjamin Peterson in <a class="reference external" href="https://bugs.python.org/issue23186">bpo-23186</a>.)
The <a class="reference internal" href="../library/ssl.html#ssl.SSLSocket.do_handshake" title="ssl.SSLSocket.do_handshake"><code class="xref py py-meth docutils literal notranslate">SSLSocket.do_handshake()</code></a>,
<a class="reference internal" href="../library/ssl.html#ssl.SSLSocket.read" title="ssl.SSLSocket.read"><code class="xref py py-meth docutils literal notranslate">SSLSocket.read()</code></a>,
<code class="xref py py-meth docutils literal notranslate">SSLSocket.shutdown()</code>, and
<a class="reference internal" href="../library/ssl.html#ssl.SSLSocket.write" title="ssl.SSLSocket.write"><code class="xref py py-meth docutils literal notranslate">SSLSocket.write()</code></a> methods of the <a class="reference internal" href="../library/ssl.html#ssl.SSLSocket" title="ssl.SSLSocket"><code class="xref py py-class docutils literal notranslate">SSLSocket</code></a>
class no longer reset the socket timeout every time bytes are received or sent.
The socket timeout is now the maximum total duration of the method.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue23853">bpo-23853</a>.)
The <a class="reference internal" href="../library/ssl.html#ssl.match_hostname" title="ssl.match_hostname"><code class="xref py py-func docutils literal notranslate">match_hostname()</code></a> function now supports matching of IP addresses.
(Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue23239">bpo-23239</a>.)
</div>
</div>
<div class="section" id="sqlite3">
<h3>sqlite3<a class="headerlink" href="#sqlite3" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/sqlite3.html#sqlite3.Row" title="sqlite3.Row"><code class="xref py py-class docutils literal notranslate">Row</code></a> class now fully supports the sequence protocol,
in particular <a class="reference internal" href="../library/functions.html#reversed" title="reversed"><code class="xref py py-func docutils literal notranslate">reversed()</code></a> iteration and slice indexing.
(Contributed by Claudiu Popa in <a class="reference external" href="https://bugs.python.org/issue10203">bpo-10203</a>; by Lucas Sinclair,
Jessica McKellar, and Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue13583">bpo-13583</a>.)
</div>
<div class="section" id="subprocess">
<h3>subprocess<a class="headerlink" href="#subprocess" title="Permalink to this headline">¶</a></h3>
The new <a class="reference internal" href="../library/subprocess.html#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate">run()</code></a> function has been added.
It runs the specified command and returns a
<a class="reference internal" href="../library/subprocess.html#subprocess.CompletedProcess" title="subprocess.CompletedProcess"><code class="xref py py-class docutils literal notranslate">CompletedProcess</code></a> object, which describes a finished
process. The new API is more consistent and is the recommended approach
to invoking subprocesses in Python code that does not need to maintain
compatibility with earlier Python versions.
(Contributed by Thomas Kluyver in <a class="reference external" href="https://bugs.python.org/issue23342">bpo-23342</a>.)
Examples:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; subprocess.run([&quot;ls&quot;, &quot;-l&quot;]) # doesn&#39;t capture output
CompletedProcess(args=[&#39;ls&#39;, &#39;-l&#39;], returncode=0)

&gt;&gt;&gt; subprocess.run(&quot;exit 1&quot;, shell=True, check=True)
Traceback (most recent call last):
 ...
subprocess.CalledProcessError: Command &#39;exit 1&#39; returned non-zero exit status 1

&gt;&gt;&gt; subprocess.run([&quot;ls&quot;, &quot;-l&quot;, &quot;/dev/null&quot;], stdout=subprocess.PIPE)
CompletedProcess(args=[&#39;ls&#39;, &#39;-l&#39;, &#39;/dev/null&#39;], returncode=0,
stdout=b&#39;crw-rw-rw- 1 root root 1, 3 Jan 23 16:23 /dev/null\n&#39;)
</pre></div>
</div>
</div>
<div class="section" id="sys">
<h3>sys<a class="headerlink" href="#sys" title="Permalink to this headline">¶</a></h3>
A new <a class="reference internal" href="../library/sys.html#sys.set_coroutine_wrapper" title="sys.set_coroutine_wrapper"><code class="xref py py-func docutils literal notranslate">set_coroutine_wrapper()</code></a> function allows setting a global
hook that will be called whenever a <a class="reference internal" href="../glossary.html#term-coroutine">coroutine object</a>
is created by an <a class="reference internal" href="../reference/compound_stmts.html#async-def"><code class="xref std std-keyword docutils literal notranslate">async def</code></a> function. A corresponding
<a class="reference internal" href="../library/sys.html#sys.get_coroutine_wrapper" title="sys.get_coroutine_wrapper"><code class="xref py py-func docutils literal notranslate">get_coroutine_wrapper()</code></a> can be used to obtain a currently set
wrapper. Both functions are <a class="reference internal" href="../glossary.html#term-provisional-api">provisional</a>,
and are intended for debugging purposes only. (Contributed by Yury Selivanov
in <a class="reference external" href="https://bugs.python.org/issue24017">bpo-24017</a>.)
A new <a class="reference internal" href="../library/sys.html#sys.is_finalizing" title="sys.is_finalizing"><code class="xref py py-func docutils literal notranslate">is_finalizing()</code></a> function can be used to check if the Python
interpreter is <a class="reference internal" href="../glossary.html#term-interpreter-shutdown">shutting down</a>.
(Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue22696">bpo-22696</a>.)
</div>
<div class="section" id="sysconfig">
<h3>sysconfig<a class="headerlink" href="#sysconfig" title="Permalink to this headline">¶</a></h3>
The name of the user scripts directory on Windows now includes the first
two components of the Python version. (Contributed by Paul Moore
in <a class="reference external" href="https://bugs.python.org/issue23437">bpo-23437</a>.)
</div>
<div class="section" id="tarfile">
<h3>tarfile<a class="headerlink" href="#tarfile" title="Permalink to this headline">¶</a></h3>
The mode argument of the <a class="reference internal" href="../library/tarfile.html#tarfile.open" title="tarfile.open"><code class="xref py py-func docutils literal notranslate">open()</code></a> function now accepts <code class="docutils literal notranslate">&quot;x&quot;</code>
to request exclusive creation. (Contributed by Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue21717">bpo-21717</a>.)
The <a class="reference internal" href="../library/tarfile.html#tarfile.TarFile.extractall" title="tarfile.TarFile.extractall"><code class="xref py py-meth docutils literal notranslate">TarFile.extractall()</code></a> and
<a class="reference internal" href="../library/tarfile.html#tarfile.TarFile.extract" title="tarfile.TarFile.extract"><code class="xref py py-meth docutils literal notranslate">TarFile.extract()</code></a> methods now take a keyword
argument numeric_owner. If set to <code class="docutils literal notranslate">True</code>, the extracted files and
directories will be owned by the numeric <code class="docutils literal notranslate">uid</code> and <code class="docutils literal notranslate">gid</code> from the tarfile.
If set to <code class="docutils literal notranslate">False</code> (the default, and the behavior in versions prior to 3.5),
they will be owned by the named user and group in the tarfile.
(Contributed by Michael Vogt and Eric Smith in <a class="reference external" href="https://bugs.python.org/issue23193">bpo-23193</a>.)
The <a class="reference internal" href="../library/tarfile.html#tarfile.TarFile.list" title="tarfile.TarFile.list"><code class="xref py py-meth docutils literal notranslate">TarFile.list()</code></a> now accepts an optional
members keyword argument that can be set to a subset of the list returned
by <a class="reference internal" href="../library/tarfile.html#tarfile.TarFile.getmembers" title="tarfile.TarFile.getmembers"><code class="xref py py-meth docutils literal notranslate">TarFile.getmembers()</code></a>.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue21549">bpo-21549</a>.)
</div>
<div class="section" id="threading">
<h3>threading<a class="headerlink" href="#threading" title="Permalink to this headline">¶</a></h3>
Both the <a class="reference internal" href="../library/threading.html#threading.Lock.acquire" title="threading.Lock.acquire"><code class="xref py py-meth docutils literal notranslate">Lock.acquire()</code></a> and
<a class="reference internal" href="../library/threading.html#threading.RLock.acquire" title="threading.RLock.acquire"><code class="xref py py-meth docutils literal notranslate">RLock.acquire()</code></a> methods
now use a monotonic clock for timeout management.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue22043">bpo-22043</a>.)
</div>
<div class="section" id="time">
<h3>time<a class="headerlink" href="#time" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/time.html#time.monotonic" title="time.monotonic"><code class="xref py py-func docutils literal notranslate">monotonic()</code></a> function is now always available.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue22043">bpo-22043</a>.)
</div>
<div class="section" id="timeit">
<h3>timeit<a class="headerlink" href="#timeit" title="Permalink to this headline">¶</a></h3>
A new command line option <code class="docutils literal notranslate">-u</code> or <code class="samp docutils literal notranslate">--unit=U</code> can be used to specify the time
unit for the timer output. Supported options are <code class="docutils literal notranslate">usec</code>, <code class="docutils literal notranslate">msec</code>,
or <code class="docutils literal notranslate">sec</code>. (Contributed by Julian Gindi in <a class="reference external" href="https://bugs.python.org/issue18983">bpo-18983</a>.)
The <a class="reference internal" href="../library/timeit.html#timeit.timeit" title="timeit.timeit"><code class="xref py py-func docutils literal notranslate">timeit()</code></a> function has a new globals parameter for
specifying the namespace in which the code will be running.
(Contributed by Ben Roberts in <a class="reference external" href="https://bugs.python.org/issue2527">bpo-2527</a>.)
</div>
<div class="section" id="tkinter">
<h3>tkinter<a class="headerlink" href="#tkinter" title="Permalink to this headline">¶</a></h3>
The <code class="xref py py-mod docutils literal notranslate">tkinter._fix</code> module used for setting up the Tcl/Tk environment
on Windows has been replaced by a private function in the <code class="xref py py-mod docutils literal notranslate">_tkinter</code>
module which makes no permanent changes to environment variables.
(Contributed by Zachary Ware in <a class="reference external" href="https://bugs.python.org/issue20035">bpo-20035</a>.)
</div>
<div class="section" id="traceback">
<h3>traceback<a class="headerlink" href="#traceback" title="Permalink to this headline">¶</a></h3>
New <a class="reference internal" href="../library/traceback.html#traceback.walk_stack" title="traceback.walk_stack"><code class="xref py py-func docutils literal notranslate">walk_stack()</code></a> and <a class="reference internal" href="../library/traceback.html#traceback.walk_tb" title="traceback.walk_tb"><code class="xref py py-func docutils literal notranslate">walk_tb()</code></a>
functions to conveniently traverse frame and traceback objects.
(Contributed by Robert Collins in <a class="reference external" href="https://bugs.python.org/issue17911">bpo-17911</a>.)
New lightweight classes: <a class="reference internal" href="../library/traceback.html#traceback.TracebackException" title="traceback.TracebackException"><code class="xref py py-class docutils literal notranslate">TracebackException</code></a>,
<a class="reference internal" href="../library/traceback.html#traceback.StackSummary" title="traceback.StackSummary"><code class="xref py py-class docutils literal notranslate">StackSummary</code></a>, and <a class="reference internal" href="../library/traceback.html#traceback.FrameSummary" title="traceback.FrameSummary"><code class="xref py py-class docutils literal notranslate">FrameSummary</code></a>.
(Contributed by Robert Collins in <a class="reference external" href="https://bugs.python.org/issue17911">bpo-17911</a>.)
Both the <a class="reference internal" href="../library/traceback.html#traceback.print_tb" title="traceback.print_tb"><code class="xref py py-func docutils literal notranslate">print_tb()</code></a> and <a class="reference internal" href="../library/traceback.html#traceback.print_stack" title="traceback.print_stack"><code class="xref py py-func docutils literal notranslate">print_stack()</code></a> functions
now support negative values for the limit argument.
(Contributed by Dmitry Kazakov in <a class="reference external" href="https://bugs.python.org/issue22619">bpo-22619</a>.)
</div>
<div class="section" id="types">
<h3>types<a class="headerlink" href="#types" title="Permalink to this headline">¶</a></h3>
A new <a class="reference internal" href="../library/types.html#types.coroutine" title="types.coroutine"><code class="xref py py-func docutils literal notranslate">coroutine()</code></a> function to transform
<a class="reference internal" href="../glossary.html#term-generator-iterator">generator</a> and
<a class="reference internal" href="../library/collections.abc.html#collections.abc.Generator" title="collections.abc.Generator"><code class="xref py py-class docutils literal notranslate">generator-like</code></a> objects into
<a class="reference internal" href="../glossary.html#term-awaitable">awaitables</a>.
(Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue24017">bpo-24017</a>.)
A new type called <a class="reference internal" href="../library/types.html#types.CoroutineType" title="types.CoroutineType"><code class="xref py py-class docutils literal notranslate">CoroutineType</code></a>, which is used for
<a class="reference internal" href="../glossary.html#term-coroutine">coroutine</a> objects created by <a class="reference internal" href="../reference/compound_stmts.html#async-def"><code class="xref std std-keyword docutils literal notranslate">async def</code></a> functions.
(Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue24400">bpo-24400</a>.)
</div>
<div class="section" id="unicodedata">
<h3>unicodedata<a class="headerlink" href="#unicodedata" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/unicodedata.html#module-unicodedata" title="unicodedata: Access the Unicode Database."><code class="xref py py-mod docutils literal notranslate">unicodedata</code></a> module now uses data from <a class="reference external" href="http://unicode.org/versions/Unicode8.0.0/">Unicode 8.0.0</a>.
</div>
<div class="section" id="unittest">
<h3>unittest<a class="headerlink" href="#unittest" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/unittest.html#unittest.TestLoader.loadTestsFromModule" title="unittest.TestLoader.loadTestsFromModule"><code class="xref py py-meth docutils literal notranslate">TestLoader.loadTestsFromModule()</code></a>
method now accepts a keyword-only argument pattern which is passed to
<code class="docutils literal notranslate">load_tests</code> as the third argument. Found packages are now checked for
<code class="docutils literal notranslate">load_tests</code> regardless of whether their path matches pattern, because it
is impossible for a package name to match the default pattern.
(Contributed by Robert Collins and Barry A. Warsaw in <a class="reference external" href="https://bugs.python.org/issue16662">bpo-16662</a>.)
Unittest discovery errors now are exposed in the
<a class="reference internal" href="../library/unittest.html#unittest.TestLoader.errors" title="unittest.TestLoader.errors"><code class="xref py py-data docutils literal notranslate">TestLoader.errors</code></a> attribute of the
<a class="reference internal" href="../library/unittest.html#unittest.TestLoader" title="unittest.TestLoader"><code class="xref py py-class docutils literal notranslate">TestLoader</code></a> instance.
(Contributed by Robert Collins in <a class="reference external" href="https://bugs.python.org/issue19746">bpo-19746</a>.)
A new command line option <code class="docutils literal notranslate">--locals</code> to show local variables in
tracebacks. (Contributed by Robert Collins in <a class="reference external" href="https://bugs.python.org/issue22936">bpo-22936</a>.)
</div>
<div class="section" id="unittest-mock">
<h3>unittest.mock<a class="headerlink" href="#unittest-mock" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/unittest.mock.html#unittest.mock.Mock" title="unittest.mock.Mock"><code class="xref py py-class docutils literal notranslate">Mock</code></a> class has the following improvements:
<ul class="simple">
<li>The class constructor has a new unsafe parameter, which causes mock
objects to raise <a class="reference internal" href="../library/exceptions.html#AttributeError" title="AttributeError"><code class="xref py py-exc docutils literal notranslate">AttributeError</code></a> on attribute names starting
with <code class="docutils literal notranslate">&quot;assert&quot;</code>.
(Contributed by Kushal Das in <a class="reference external" href="https://bugs.python.org/issue21238">bpo-21238</a>.)</li>
<li>A new <a class="reference internal" href="../library/unittest.mock.html#unittest.mock.Mock.assert_not_called" title="unittest.mock.Mock.assert_not_called"><code class="xref py py-meth docutils literal notranslate">Mock.assert_not_called()</code></a>
method to check if the mock object was called.
(Contributed by Kushal Das in <a class="reference external" href="https://bugs.python.org/issue21262">bpo-21262</a>.)</li>
</ul>
The <a class="reference internal" href="../library/unittest.mock.html#unittest.mock.MagicMock" title="unittest.mock.MagicMock"><code class="xref py py-class docutils literal notranslate">MagicMock</code></a> class now supports <a class="reference internal" href="../reference/datamodel.html#object.__truediv__" title="object.__truediv__"><code class="xref py py-meth docutils literal notranslate">__truediv__()</code></a>,
<a class="reference internal" href="../reference/datamodel.html#object.__divmod__" title="object.__divmod__"><code class="xref py py-meth docutils literal notranslate">__divmod__()</code></a> and <a class="reference internal" href="../reference/datamodel.html#object.__matmul__" title="object.__matmul__"><code class="xref py py-meth docutils literal notranslate">__matmul__()</code></a> operators.
(Contributed by Johannes Baiter in <a class="reference external" href="https://bugs.python.org/issue20968">bpo-20968</a>, and Håkan Lövdahl
in <a class="reference external" href="https://bugs.python.org/issue23581">bpo-23581</a> and <a class="reference external" href="https://bugs.python.org/issue23568">bpo-23568</a>.)
It is no longer necessary to explicitly pass <code class="docutils literal notranslate">create=True</code> to the
<a class="reference internal" href="../library/unittest.mock.html#unittest.mock.patch" title="unittest.mock.patch"><code class="xref py py-func docutils literal notranslate">patch()</code></a> function when patching builtin names.
(Contributed by Kushal Das in <a class="reference external" href="https://bugs.python.org/issue17660">bpo-17660</a>.)
</div>
<div class="section" id="urllib">
<h3>urllib<a class="headerlink" href="#urllib" title="Permalink to this headline">¶</a></h3>
A new
<a class="reference internal" href="../library/urllib.request.html#urllib.request.HTTPPasswordMgrWithPriorAuth" title="urllib.request.HTTPPasswordMgrWithPriorAuth"><code class="xref py py-class docutils literal notranslate">request.HTTPPasswordMgrWithPriorAuth</code></a>
class allows HTTP Basic Authentication credentials to be managed so as to
eliminate unnecessary <code class="docutils literal notranslate">401</code> response handling, or to unconditionally send
credentials on the first request in order to communicate with servers that
return a <code class="docutils literal notranslate">404</code> response instead of a <code class="docutils literal notranslate">401</code> if the <code class="docutils literal notranslate">Authorization</code> header
is not sent. (Contributed by Matej Cepl in <a class="reference external" href="https://bugs.python.org/issue19494">bpo-19494</a> and Akshit Khurana in
<a class="reference external" href="https://bugs.python.org/issue7159">bpo-7159</a>.)
A new quote_via argument for the
<a class="reference internal" href="../library/urllib.parse.html#urllib.parse.urlencode" title="urllib.parse.urlencode"><code class="xref py py-func docutils literal notranslate">parse.urlencode()</code></a>
function provides a way to control the encoding of query parts if needed.
(Contributed by Samwyse and Arnon Yaari in <a class="reference external" href="https://bugs.python.org/issue13866">bpo-13866</a>.)
The <a class="reference internal" href="../library/urllib.request.html#urllib.request.urlopen" title="urllib.request.urlopen"><code class="xref py py-func docutils literal notranslate">request.urlopen()</code></a> function accepts an
<a class="reference internal" href="../library/ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate">ssl.SSLContext</code></a> object as a context argument, which will be used for
the HTTPS connection. (Contributed by Alex Gaynor in <a class="reference external" href="https://bugs.python.org/issue22366">bpo-22366</a>.)
The <a class="reference internal" href="../library/urllib.parse.html#urllib.parse.urljoin" title="urllib.parse.urljoin"><code class="xref py py-func docutils literal notranslate">parse.urljoin()</code></a> was updated to use the
<a class="rfc reference external" href="https://tools.ietf.org/html/rfc3986.html">RFC 3986</a> semantics for the resolution of relative URLs, rather than
<a class="rfc reference external" href="https://tools.ietf.org/html/rfc1808.html">RFC 1808</a> and <a class="rfc reference external" href="https://tools.ietf.org/html/rfc2396.html">RFC 2396</a>.
(Contributed by Demian Brecht and Senthil Kumaran in <a class="reference external" href="https://bugs.python.org/issue22118">bpo-22118</a>.)
</div>
<div class="section" id="wsgiref">
<h3>wsgiref<a class="headerlink" href="#wsgiref" title="Permalink to this headline">¶</a></h3>
The headers argument of the <a class="reference internal" href="../library/wsgiref.html#wsgiref.headers.Headers" title="wsgiref.headers.Headers"><code class="xref py py-class docutils literal notranslate">headers.Headers</code></a>
class constructor is now optional.
(Contributed by Pablo Torres Navarrete and SilentGhost in <a class="reference external" href="https://bugs.python.org/issue5800">bpo-5800</a>.)
</div>
<div class="section" id="xmlrpc">
<h3>xmlrpc<a class="headerlink" href="#xmlrpc" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/xmlrpc.client.html#xmlrpc.client.ServerProxy" title="xmlrpc.client.ServerProxy"><code class="xref py py-class docutils literal notranslate">client.ServerProxy</code></a> class now supports
the <a class="reference internal" href="../glossary.html#term-context-manager">context manager</a> protocol.
(Contributed by Claudiu Popa in <a class="reference external" href="https://bugs.python.org/issue20627">bpo-20627</a>.)
The <a class="reference internal" href="../library/xmlrpc.client.html#xmlrpc.client.ServerProxy" title="xmlrpc.client.ServerProxy"><code class="xref py py-class docutils literal notranslate">client.ServerProxy</code></a> constructor now accepts
an optional <a class="reference internal" href="../library/ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate">ssl.SSLContext</code></a> instance.
(Contributed by Alex Gaynor in <a class="reference external" href="https://bugs.python.org/issue22960">bpo-22960</a>.)
</div>
<div class="section" id="xml-sax">
<h3>xml.sax<a class="headerlink" href="#xml-sax" title="Permalink to this headline">¶</a></h3>
SAX parsers now support a character stream of the
<a class="reference internal" href="../library/xml.sax.reader.html#xml.sax.xmlreader.InputSource" title="xml.sax.xmlreader.InputSource"><code class="xref py py-class docutils literal notranslate">xmlreader.InputSource</code></a> object.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue2175">bpo-2175</a>.)
<a class="reference internal" href="../library/xml.sax.html#xml.sax.parseString" title="xml.sax.parseString"><code class="xref py py-func docutils literal notranslate">parseString()</code></a> now accepts a <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> instance.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue10590">bpo-10590</a>.)
</div>
<div class="section" id="zipfile">
<h3>zipfile<a class="headerlink" href="#zipfile" title="Permalink to this headline">¶</a></h3>
ZIP output can now be written to unseekable streams.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue23252">bpo-23252</a>.)
The mode argument of <a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile.open" title="zipfile.ZipFile.open"><code class="xref py py-meth docutils literal notranslate">ZipFile.open()</code></a> method now
accepts <code class="docutils literal notranslate">&quot;x&quot;</code> to request exclusive creation.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue21717">bpo-21717</a>.)
</div>
</div>
<div class="section" id="other-module-level-changes">
<h2>Other module-level changes<a class="headerlink" href="#other-module-level-changes" title="Permalink to this headline">¶</a></h2>
Many functions in the <a class="reference internal" href="../library/mmap.html#module-mmap" title="mmap: Interface to memory-mapped files for Unix and Windows."><code class="xref py py-mod docutils literal notranslate">mmap</code></a>, <a class="reference internal" href="../library/ossaudiodev.html#module-ossaudiodev" title="ossaudiodev: Access to OSS-compatible audio devices. (Linux, FreeBSD)"><code class="xref py py-mod docutils literal notranslate">ossaudiodev</code></a>, <a class="reference internal" href="../library/socket.html#module-socket" title="socket: Low-level networking interface."><code class="xref py py-mod docutils literal notranslate">socket</code></a>,
<a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate">ssl</code></a>, and <a class="reference internal" href="../library/codecs.html#module-codecs" title="codecs: Encode and decode data and streams."><code class="xref py py-mod docutils literal notranslate">codecs</code></a> modules now accept writable
<a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like objects</a>.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue23001">bpo-23001</a>.)
</div>
<div class="section" id="optimizations">
<h2>Optimizations<a class="headerlink" href="#optimizations" title="Permalink to this headline">¶</a></h2>
The <a class="reference internal" href="../library/os.html#os.walk" title="os.walk"><code class="xref py py-func docutils literal notranslate">os.walk()</code></a> function has been sped up by 3 to 5 times on POSIX systems,
and by 7 to 20 times on Windows. This was done using the new <a class="reference internal" href="../library/os.html#os.scandir" title="os.scandir"><code class="xref py py-func docutils literal notranslate">os.scandir()</code></a>
function, which exposes file information from the underlying <code class="docutils literal notranslate">readdir</code> or
<code class="docutils literal notranslate">FindFirstFile</code>/<code class="docutils literal notranslate">FindNextFile</code> system calls. (Contributed by
Ben Hoyt with help from Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue23605">bpo-23605</a>.)
Construction of <code class="docutils literal notranslate">bytes(int)</code> (filled by zero bytes) is faster and uses less
memory for large objects. <code class="docutils literal notranslate">calloc()</code> is used instead of <code class="docutils literal notranslate">malloc()</code> to
allocate memory for these objects.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue21233">bpo-21233</a>.)
Some operations on <a class="reference internal" href="../library/ipaddress.html#module-ipaddress" title="ipaddress: IPv4/IPv6 manipulation library."><code class="xref py py-mod docutils literal notranslate">ipaddress</code></a> <a class="reference internal" href="../library/ipaddress.html#ipaddress.IPv4Network" title="ipaddress.IPv4Network"><code class="xref py py-class docutils literal notranslate">IPv4Network</code></a> and
<a class="reference internal" href="../library/ipaddress.html#ipaddress.IPv6Network" title="ipaddress.IPv6Network"><code class="xref py py-class docutils literal notranslate">IPv6Network</code></a> have been massively sped up, such as
<a class="reference internal" href="../library/ipaddress.html#ipaddress.IPv4Network.subnets" title="ipaddress.IPv4Network.subnets"><code class="xref py py-meth docutils literal notranslate">subnets()</code></a>, <a class="reference internal" href="../library/ipaddress.html#ipaddress.IPv4Network.supernet" title="ipaddress.IPv4Network.supernet"><code class="xref py py-meth docutils literal notranslate">supernet()</code></a>,
<a class="reference internal" href="../library/ipaddress.html#ipaddress.summarize_address_range" title="ipaddress.summarize_address_range"><code class="xref py py-func docutils literal notranslate">summarize_address_range()</code></a>, <a class="reference internal" href="../library/ipaddress.html#ipaddress.collapse_addresses" title="ipaddress.collapse_addresses"><code class="xref py py-func docutils literal notranslate">collapse_addresses()</code></a>.
The speed up can range from 3 to 15 times.
(Contributed by Antoine Pitrou, Michel Albert, and Markus in
<a class="reference external" href="https://bugs.python.org/issue21486">bpo-21486</a>, <a class="reference external" href="https://bugs.python.org/issue21487">bpo-21487</a>, <a class="reference external" href="https://bugs.python.org/issue20826">bpo-20826</a>, <a class="reference external" href="https://bugs.python.org/issue23266">bpo-23266</a>.)
Pickling of <a class="reference internal" href="../library/ipaddress.html#module-ipaddress" title="ipaddress: IPv4/IPv6 manipulation library."><code class="xref py py-mod docutils literal notranslate">ipaddress</code></a> objects was optimized to produce significantly
smaller output. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue23133">bpo-23133</a>.)
Many operations on <a class="reference internal" href="../library/io.html#io.BytesIO" title="io.BytesIO"><code class="xref py py-class docutils literal notranslate">io.BytesIO</code></a> are now 50% to 100% faster.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue15381">bpo-15381</a> and David Wilson in
<a class="reference external" href="https://bugs.python.org/issue22003">bpo-22003</a>.)
The <a class="reference internal" href="../library/marshal.html#marshal.dumps" title="marshal.dumps"><code class="xref py py-func docutils literal notranslate">marshal.dumps()</code></a> function is now faster: 65–85% with versions 3
and 4, 20–25% with versions 0 to 2 on typical data, and up to 5 times in
best cases.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue20416">bpo-20416</a> and <a class="reference external" href="https://bugs.python.org/issue23344">bpo-23344</a>.)
The UTF-32 encoder is now 3 to 7 times faster.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue15027">bpo-15027</a>.)
Regular expressions are now parsed up to 10% faster.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue19380">bpo-19380</a>.)
The <a class="reference internal" href="../library/json.html#json.dumps" title="json.dumps"><code class="xref py py-func docutils literal notranslate">json.dumps()</code></a> function was optimized to run with
<code class="docutils literal notranslate">ensure_ascii=False</code> as fast as with <code class="docutils literal notranslate">ensure_ascii=True</code>.
(Contributed by Naoki Inada in <a class="reference external" href="https://bugs.python.org/issue23206">bpo-23206</a>.)
The <a class="reference internal" href="../c-api/object.html#c.PyObject_IsInstance" title="PyObject_IsInstance"><code class="xref c c-func docutils literal notranslate">PyObject_IsInstance()</code></a> and <a class="reference internal" href="../c-api/object.html#c.PyObject_IsSubclass" title="PyObject_IsSubclass"><code class="xref c c-func docutils literal notranslate">PyObject_IsSubclass()</code></a>
functions have been sped up in the common case that the second argument
has <a class="reference internal" href="../library/functions.html#type" title="type"><code class="xref py py-class docutils literal notranslate">type</code></a> as its metaclass.
(Contributed Georg Brandl by in <a class="reference external" href="https://bugs.python.org/issue22540">bpo-22540</a>.)
Method caching was slightly improved, yielding up to 5% performance
improvement in some benchmarks.
(Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue22847">bpo-22847</a>.)
Objects from the <a class="reference internal" href="../library/random.html#module-random" title="random: Generate pseudo-random numbers with various common distributions."><code class="xref py py-mod docutils literal notranslate">random</code></a> module now use 50% less memory on 64-bit
builds. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue23488">bpo-23488</a>.)
The <a class="reference internal" href="../library/functions.html#property" title="property"><code class="xref py py-func docutils literal notranslate">property()</code></a> getter calls are up to 25% faster.
(Contributed by Joe Jevnik in <a class="reference external" href="https://bugs.python.org/issue23910">bpo-23910</a>.)
Instantiation of <a class="reference internal" href="../library/fractions.html#fractions.Fraction" title="fractions.Fraction"><code class="xref py py-class docutils literal notranslate">fractions.Fraction</code></a> is now up to 30% faster.
(Contributed by Stefan Behnel in <a class="reference external" href="https://bugs.python.org/issue22464">bpo-22464</a>.)
String methods <a class="reference internal" href="../library/stdtypes.html#str.find" title="str.find"><code class="xref py py-meth docutils literal notranslate">find()</code></a>, <a class="reference internal" href="../library/stdtypes.html#str.rfind" title="str.rfind"><code class="xref py py-meth docutils literal notranslate">rfind()</code></a>, <a class="reference internal" href="../library/stdtypes.html#str.split" title="str.split"><code class="xref py py-meth docutils literal notranslate">split()</code></a>,
<a class="reference internal" href="../library/stdtypes.html#str.partition" title="str.partition"><code class="xref py py-meth docutils literal notranslate">partition()</code></a> and the <a class="reference internal" href="../reference/expressions.html#in"><code class="xref std std-keyword docutils literal notranslate">in</code></a> string operator are now significantly
faster for searching 1-character substrings.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue23573">bpo-23573</a>.)
</div>
<div class="section" id="build-and-c-api-changes">
<h2>Build and C API Changes<a class="headerlink" href="#build-and-c-api-changes" title="Permalink to this headline">¶</a></h2>
New <code class="docutils literal notranslate">calloc</code> functions were added:
<ul class="simple">
<li><a class="reference internal" href="../c-api/memory.html#c.PyMem_RawCalloc" title="PyMem_RawCalloc"><code class="xref c c-func docutils literal notranslate">PyMem_RawCalloc()</code></a>,</li>
<li><a class="reference internal" href="../c-api/memory.html#c.PyMem_Calloc" title="PyMem_Calloc"><code class="xref c c-func docutils literal notranslate">PyMem_Calloc()</code></a>,</li>
<li><a class="reference internal" href="../c-api/memory.html#c.PyObject_Calloc" title="PyObject_Calloc"><code class="xref c c-func docutils literal notranslate">PyObject_Calloc()</code></a>.</li>
</ul>
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue21233">bpo-21233</a>.)
New encoding/decoding helper functions:
<ul class="simple">
<li><a class="reference internal" href="../c-api/sys.html#c.Py_DecodeLocale" title="Py_DecodeLocale"><code class="xref c c-func docutils literal notranslate">Py_DecodeLocale()</code></a> (replaced <code class="docutils literal notranslate">_Py_char2wchar()</code>),</li>
<li><a class="reference internal" href="../c-api/sys.html#c.Py_EncodeLocale" title="Py_EncodeLocale"><code class="xref c c-func docutils literal notranslate">Py_EncodeLocale()</code></a> (replaced <code class="docutils literal notranslate">_Py_wchar2char()</code>).</li>
</ul>
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue18395">bpo-18395</a>.)
A new <a class="reference internal" href="../c-api/codec.html#c.PyCodec_NameReplaceErrors" title="PyCodec_NameReplaceErrors"><code class="xref c c-func docutils literal notranslate">PyCodec_NameReplaceErrors()</code></a> function to replace the unicode
encode error with <code class="docutils literal notranslate">\N{...}</code> escapes.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue19676">bpo-19676</a>.)
A new <a class="reference internal" href="../c-api/exceptions.html#c.PyErr_FormatV" title="PyErr_FormatV"><code class="xref c c-func docutils literal notranslate">PyErr_FormatV()</code></a> function similar to <a class="reference internal" href="../c-api/exceptions.html#c.PyErr_Format" title="PyErr_Format"><code class="xref c c-func docutils literal notranslate">PyErr_Format()</code></a>,
but accepts a <code class="docutils literal notranslate">va_list</code> argument.
(Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue18711">bpo-18711</a>.)
A new <code class="xref c c-data docutils literal notranslate">PyExc_RecursionError</code> exception.
(Contributed by Georg Brandl in <a class="reference external" href="https://bugs.python.org/issue19235">bpo-19235</a>.)
New <a class="reference internal" href="../c-api/module.html#c.PyModule_FromDefAndSpec" title="PyModule_FromDefAndSpec"><code class="xref c c-func docutils literal notranslate">PyModule_FromDefAndSpec()</code></a>, <a class="reference internal" href="../c-api/module.html#c.PyModule_FromDefAndSpec2" title="PyModule_FromDefAndSpec2"><code class="xref c c-func docutils literal notranslate">PyModule_FromDefAndSpec2()</code></a>,
and <a class="reference internal" href="../c-api/module.html#c.PyModule_ExecDef" title="PyModule_ExecDef"><code class="xref c c-func docutils literal notranslate">PyModule_ExecDef()</code></a> functions introduced by <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0489">PEP 489</a> –
multi-phase extension module initialization.
(Contributed by Petr Viktorin in <a class="reference external" href="https://bugs.python.org/issue24268">bpo-24268</a>.)
New <a class="reference internal" href="../c-api/number.html#c.PyNumber_MatrixMultiply" title="PyNumber_MatrixMultiply"><code class="xref c c-func docutils literal notranslate">PyNumber_MatrixMultiply()</code></a> and
<a class="reference internal" href="../c-api/number.html#c.PyNumber_InPlaceMatrixMultiply" title="PyNumber_InPlaceMatrixMultiply"><code class="xref c c-func docutils literal notranslate">PyNumber_InPlaceMatrixMultiply()</code></a> functions to perform matrix
multiplication.
(Contributed by Benjamin Peterson in <a class="reference external" href="https://bugs.python.org/issue21176">bpo-21176</a>. See also <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0465">PEP 465</a>
for details.)
The <a class="reference internal" href="../c-api/typeobj.html#c.PyTypeObject.tp_finalize" title="PyTypeObject.tp_finalize"><code class="xref c c-member docutils literal notranslate">PyTypeObject.tp_finalize</code></a> slot is now part of the stable ABI.
Windows builds now require Microsoft Visual C++ 14.0, which
is available as part of <a class="reference external" href="https://www.visualstudio.com/">Visual Studio 2015</a>.
Extension modules now include a platform information tag in their filename on
some platforms (the tag is optional, and CPython will import extensions without
it, although if the tag is present and mismatched, the extension won’t be
loaded):
<ul class="simple">
<li>On Linux, extension module filenames end with
<code class="docutils literal notranslate">.cpython-&lt;major&gt;&lt;minor&gt;m-&lt;architecture&gt;-&lt;os&gt;.pyd</code>:<ul>
<li><code class="docutils literal notranslate">&lt;major&gt;</code> is the major number of the Python version;
for Python 3.5 this is <code class="docutils literal notranslate">3</code>.</li>
<li><code class="docutils literal notranslate">&lt;minor&gt;</code> is the minor number of the Python version;
for Python 3.5 this is <code class="docutils literal notranslate">5</code>.</li>
<li><code class="docutils literal notranslate">&lt;architecture&gt;</code> is the hardware architecture the extension module
was built to run on. It’s most commonly either <code class="docutils literal notranslate">i386</code> for 32-bit Intel
platforms or <code class="docutils literal notranslate">x86_64</code> for 64-bit Intel (and AMD) platforms.</li>
<li><code class="docutils literal notranslate">&lt;os&gt;</code> is always <code class="docutils literal notranslate">linux-gnu</code>, except for extensions built to
talk to the 32-bit ABI on 64-bit platforms, in which case it is
<code class="docutils literal notranslate">linux-gnu32</code> (and <code class="docutils literal notranslate">&lt;architecture&gt;</code> will be <code class="docutils literal notranslate">x86_64</code>).</li>
</ul>
</li>
<li>On Windows, extension module filenames end with
<code class="docutils literal notranslate">&lt;debug&gt;.cp&lt;major&gt;&lt;minor&gt;-&lt;platform&gt;.pyd</code>:<ul>
<li><code class="docutils literal notranslate">&lt;major&gt;</code> is the major number of the Python version;
for Python 3.5 this is <code class="docutils literal notranslate">3</code>.</li>
<li><code class="docutils literal notranslate">&lt;minor&gt;</code> is the minor number of the Python version;
for Python 3.5 this is <code class="docutils literal notranslate">5</code>.</li>
<li><code class="docutils literal notranslate">&lt;platform&gt;</code> is the platform the extension module was built for,
either <code class="docutils literal notranslate">win32</code> for Win32, <code class="docutils literal notranslate">win_amd64</code> for Win64, <code class="docutils literal notranslate">win_ia64</code> for
Windows Itanium 64, and <code class="docutils literal notranslate">win_arm</code> for Windows on ARM.</li>
<li>If built in debug mode, <code class="docutils literal notranslate">&lt;debug&gt;</code> will be <code class="docutils literal notranslate">_d</code>,
otherwise it will be blank.</li>
</ul>
</li>
<li>On OS X platforms, extension module filenames now end with <code class="docutils literal notranslate">-darwin.so</code>.</li>
<li>On all other platforms, extension module filenames are the same as they were
with Python 3.4.</li>
</ul>
</div>
<div class="section" id="deprecated">
<h2>Deprecated<a class="headerlink" href="#deprecated" title="Permalink to this headline">¶</a></h2>
<div class="section" id="new-keywords">
<h3>New Keywords<a class="headerlink" href="#new-keywords" title="Permalink to this headline">¶</a></h3>
<code class="docutils literal notranslate">async</code> and <code class="docutils literal notranslate">await</code> are not recommended to be used as variable, class,
function or module names. Introduced by <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0492">PEP 492</a> in Python 3.5, they will
become proper keywords in Python 3.7.
</div>
<div class="section" id="deprecated-python-behavior">
<h3>Deprecated Python Behavior<a class="headerlink" href="#deprecated-python-behavior" title="Permalink to this headline">¶</a></h3>
Raising the <a class="reference internal" href="../library/exceptions.html#StopIteration" title="StopIteration"><code class="xref py py-exc docutils literal notranslate">StopIteration</code></a> exception inside a generator will now generate a silent
<a class="reference internal" href="../library/exceptions.html#PendingDeprecationWarning" title="PendingDeprecationWarning"><code class="xref py py-exc docutils literal notranslate">PendingDeprecationWarning</code></a>, which will become a non-silent deprecation
warning in Python 3.6 and will trigger a <a class="reference internal" href="../library/exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate">RuntimeError</code></a> in Python 3.7.
See <a class="reference internal" href="#whatsnew-pep-479">PEP 479: Change StopIteration handling inside generators</a>
for details.
</div>
<div class="section" id="unsupported-operating-systems">
<h3>Unsupported Operating Systems<a class="headerlink" href="#unsupported-operating-systems" title="Permalink to this headline">¶</a></h3>
Windows XP is no longer supported by Microsoft, thus, per <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0011">PEP 11</a>, CPython
3.5 is no longer officially supported on this OS.
</div>
<div class="section" id="deprecated-python-modules-functions-and-methods">
<h3>Deprecated Python modules, functions and methods<a class="headerlink" href="#deprecated-python-modules-functions-and-methods" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/formatter.html#module-formatter" title="formatter: Generic output formatter and device interface. (deprecated)"><code class="xref py py-mod docutils literal notranslate">formatter</code></a> module has now graduated to full deprecation and is still
slated for removal in Python 3.6.
The <a class="reference internal" href="../library/asyncio-task.html#asyncio.async" title="asyncio.async"><code class="xref py py-func docutils literal notranslate">asyncio.async()</code></a> function is deprecated in favor of
<a class="reference internal" href="../library/asyncio-task.html#asyncio.ensure_future" title="asyncio.ensure_future"><code class="xref py py-func docutils literal notranslate">ensure_future()</code></a>.
The <a class="reference internal" href="../library/smtpd.html#module-smtpd" title="smtpd: A SMTP server implementation in Python."><code class="xref py py-mod docutils literal notranslate">smtpd</code></a> module has in the past always decoded the DATA portion of
email messages using the <code class="docutils literal notranslate">utf-8</code> codec. This can now be controlled by the
new decode_data keyword to <a class="reference internal" href="../library/smtpd.html#smtpd.SMTPServer" title="smtpd.SMTPServer"><code class="xref py py-class docutils literal notranslate">SMTPServer</code></a>. The default value is
<code class="docutils literal notranslate">True</code>, but this default is deprecated. Specify the decode_data keyword
with an appropriate value to avoid the deprecation warning.
Directly assigning values to the <a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel.key" title="http.cookies.Morsel.key"><code class="xref py py-attr docutils literal notranslate">key</code></a>,
<a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel.value" title="http.cookies.Morsel.value"><code class="xref py py-attr docutils literal notranslate">value</code></a> and
<a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel.coded_value" title="http.cookies.Morsel.coded_value"><code class="xref py py-attr docutils literal notranslate">coded_value</code></a> of <a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel" title="http.cookies.Morsel"><code class="xref py py-class docutils literal notranslate">http.cookies.Morsel</code></a>
objects is deprecated. Use the <a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel.set" title="http.cookies.Morsel.set"><code class="xref py py-meth docutils literal notranslate">set()</code></a> method
instead. In addition, the undocumented LegalChars parameter of
<a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel.set" title="http.cookies.Morsel.set"><code class="xref py py-meth docutils literal notranslate">set()</code></a> is deprecated, and is now ignored.
Passing a format string as keyword argument format_string to the
<a class="reference internal" href="../library/string.html#string.Formatter.format" title="string.Formatter.format"><code class="xref py py-meth docutils literal notranslate">format()</code></a> method of the <a class="reference internal" href="../library/string.html#string.Formatter" title="string.Formatter"><code class="xref py py-class docutils literal notranslate">string.Formatter</code></a>
class has been deprecated.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue23671">bpo-23671</a>.)
The <a class="reference internal" href="../library/platform.html#platform.dist" title="platform.dist"><code class="xref py py-func docutils literal notranslate">platform.dist()</code></a> and <a class="reference internal" href="../library/platform.html#platform.linux_distribution" title="platform.linux_distribution"><code class="xref py py-func docutils literal notranslate">platform.linux_distribution()</code></a> functions
are now deprecated. Linux distributions use too many different ways of
describing themselves, so the functionality is left to a package.
(Contributed by Vajrasky Kok and Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue1322">bpo-1322</a>.)
The previously undocumented <code class="docutils literal notranslate">from_function</code> and <code class="docutils literal notranslate">from_builtin</code> methods of
<a class="reference internal" href="../library/inspect.html#inspect.Signature" title="inspect.Signature"><code class="xref py py-class docutils literal notranslate">inspect.Signature</code></a> are deprecated. Use the new
<a class="reference internal" href="../library/inspect.html#inspect.Signature.from_callable" title="inspect.Signature.from_callable"><code class="xref py py-meth docutils literal notranslate">Signature.from_callable()</code></a>
method instead. (Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue24248">bpo-24248</a>.)
The <a class="reference internal" href="../library/inspect.html#inspect.getargspec" title="inspect.getargspec"><code class="xref py py-func docutils literal notranslate">inspect.getargspec()</code></a> function is deprecated and scheduled to be
removed in Python 3.6. (See <a class="reference external" href="https://bugs.python.org/issue20438">bpo-20438</a> for details.)
The <a class="reference internal" href="../library/inspect.html#module-inspect" title="inspect: Extract information and source code from live objects."><code class="xref py py-mod docutils literal notranslate">inspect</code></a> <a class="reference internal" href="../library/inspect.html#inspect.getfullargspec" title="inspect.getfullargspec"><code class="xref py py-func docutils literal notranslate">getfullargspec()</code></a>,
<a class="reference internal" href="../library/inspect.html#inspect.getcallargs" title="inspect.getcallargs"><code class="xref py py-func docutils literal notranslate">getcallargs()</code></a>, and <a class="reference internal" href="../library/inspect.html#inspect.formatargspec" title="inspect.formatargspec"><code class="xref py py-func docutils literal notranslate">formatargspec()</code></a> functions are
deprecated in favor of the <a class="reference internal" href="../library/inspect.html#inspect.signature" title="inspect.signature"><code class="xref py py-func docutils literal notranslate">inspect.signature()</code></a> API. (Contributed by Yury
Selivanov in <a class="reference external" href="https://bugs.python.org/issue20438">bpo-20438</a>.)
<a class="reference internal" href="../library/inspect.html#inspect.getargvalues" title="inspect.getargvalues"><code class="xref py py-func docutils literal notranslate">getargvalues()</code></a> and <a class="reference internal" href="../library/inspect.html#inspect.formatargvalues" title="inspect.formatargvalues"><code class="xref py py-func docutils literal notranslate">formatargvalues()</code></a> functions
were inadvertently marked as deprecated with the release of Python 3.5.0.
Use of <a class="reference internal" href="../library/re.html#re.LOCALE" title="re.LOCALE"><code class="xref py py-const docutils literal notranslate">re.LOCALE</code></a> flag with str patterns or <a class="reference internal" href="../library/re.html#re.ASCII" title="re.ASCII"><code class="xref py py-const docutils literal notranslate">re.ASCII</code></a> is now
deprecated. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue22407">bpo-22407</a>.)
Use of unrecognized special sequences consisting of <code class="docutils literal notranslate">'\'</code> and an ASCII letter
in regular expression patterns and replacement patterns now raises a
deprecation warning and will be forbidden in Python 3.6.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue23622">bpo-23622</a>.)
The undocumented and unofficial use_load_tests default argument of the
<a class="reference internal" href="../library/unittest.html#unittest.TestLoader.loadTestsFromModule" title="unittest.TestLoader.loadTestsFromModule"><code class="xref py py-meth docutils literal notranslate">unittest.TestLoader.loadTestsFromModule()</code></a> method now is
deprecated and ignored.
(Contributed by Robert Collins and Barry A. Warsaw in <a class="reference external" href="https://bugs.python.org/issue16662">bpo-16662</a>.)
</div>
</div>
<div class="section" id="removed">
<h2>Removed<a class="headerlink" href="#removed" title="Permalink to this headline">¶</a></h2>
<div class="section" id="api-and-feature-removals">
<h3>API and Feature Removals<a class="headerlink" href="#api-and-feature-removals" title="Permalink to this headline">¶</a></h3>
The following obsolete and previously deprecated APIs and features have been
removed:
<ul class="simple">
<li>The <code class="docutils literal notranslate">__version__</code> attribute has been dropped from the email package. The
email code hasn’t been shipped separately from the stdlib for a long time,
and the <code class="docutils literal notranslate">__version__</code> string was not updated in the last few releases.</li>
<li>The internal <code class="docutils literal notranslate">Netrc</code> class in the <a class="reference internal" href="../library/ftplib.html#module-ftplib" title="ftplib: FTP protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">ftplib</code></a> module was deprecated in
3.4, and has now been removed.
(Contributed by Matt Chaput in <a class="reference external" href="https://bugs.python.org/issue6623">bpo-6623</a>.)</li>
<li>The concept of <code class="docutils literal notranslate">.pyo</code> files has been removed.</li>
<li>The JoinableQueue class in the provisional <a class="reference internal" href="../library/asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O, event loop, coroutines and tasks."><code class="xref py py-mod docutils literal notranslate">asyncio</code></a> module was
deprecated in 3.4.4 and is now removed.
(Contributed by A. Jesse Jiryu Davis in <a class="reference external" href="https://bugs.python.org/issue23464">bpo-23464</a>.)</li>
</ul>
</div>
</div>
<div class="section" id="porting-to-python-3-5">
<h2>Porting to Python 3.5<a class="headerlink" href="#porting-to-python-3-5" title="Permalink to this headline">¶</a></h2>
This section lists previously described changes and other bugfixes
that may require changes to your code.
<div class="section" id="changes-in-python-behavior">
<h3>Changes in Python behavior<a class="headerlink" href="#changes-in-python-behavior" title="Permalink to this headline">¶</a></h3>
<ul>
<li>Due to an oversight, earlier Python versions erroneously accepted the
following syntax:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>f(1 for x in [1], *args)
f(1 for x in [1], **kwargs)
</pre></div>
</div>
Python 3.5 now correctly raises a <a class="reference internal" href="../library/exceptions.html#SyntaxError" title="SyntaxError"><code class="xref py py-exc docutils literal notranslate">SyntaxError</code></a>, as generator
expressions must be put in parentheses if not a sole argument to a function.
</li>
</ul>
</div>
<div class="section" id="changes-in-the-python-api">
<h3>Changes in the Python API<a class="headerlink" href="#changes-in-the-python-api" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0475">PEP 475</a>: System calls are now retried when interrupted by a signal instead
of raising <a class="reference internal" href="../library/exceptions.html#InterruptedError" title="InterruptedError"><code class="xref py py-exc docutils literal notranslate">InterruptedError</code></a> if the Python signal handler does not
raise an exception.</li>
<li>Before Python 3.5, a <a class="reference internal" href="../library/datetime.html#datetime.time" title="datetime.time"><code class="xref py py-class docutils literal notranslate">datetime.time</code></a> object was considered to be false
if it represented midnight in UTC. This behavior was considered obscure and
error-prone and has been removed in Python 3.5. See <a class="reference external" href="https://bugs.python.org/issue13936">bpo-13936</a> for full
details.</li>
<li>The <code class="xref py py-meth docutils literal notranslate">ssl.SSLSocket.send()</code> method now raises either
<a class="reference internal" href="../library/ssl.html#ssl.SSLWantReadError" title="ssl.SSLWantReadError"><code class="xref py py-exc docutils literal notranslate">ssl.SSLWantReadError</code></a> or <a class="reference internal" href="../library/ssl.html#ssl.SSLWantWriteError" title="ssl.SSLWantWriteError"><code class="xref py py-exc docutils literal notranslate">ssl.SSLWantWriteError</code></a>
on a non-blocking socket if the operation would block. Previously,
it would return <code class="docutils literal notranslate">0</code>. (Contributed by Nikolaus Rath in <a class="reference external" href="https://bugs.python.org/issue20951">bpo-20951</a>.)</li>
<li>The <code class="docutils literal notranslate">__name__</code> attribute of generators is now set from the function name,
instead of being set from the code name. Use <code class="docutils literal notranslate">gen.gi_code.co_name</code> to
retrieve the code name. Generators also have a new <code class="docutils literal notranslate">__qualname__</code>
attribute, the qualified name, which is now used for the representation
of a generator (<code class="docutils literal notranslate">repr(gen)</code>).
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue21205">bpo-21205</a>.)</li>
<li>The deprecated “strict” mode and argument of <a class="reference internal" href="../library/html.parser.html#html.parser.HTMLParser" title="html.parser.HTMLParser"><code class="xref py py-class docutils literal notranslate">HTMLParser</code></a>,
<code class="xref py py-meth docutils literal notranslate">HTMLParser.error()</code>, and the <code class="xref py py-exc docutils literal notranslate">HTMLParserError</code> exception have been
removed. (Contributed by Ezio Melotti in <a class="reference external" href="https://bugs.python.org/issue15114">bpo-15114</a>.)
The convert_charrefs argument of <a class="reference internal" href="../library/html.parser.html#html.parser.HTMLParser" title="html.parser.HTMLParser"><code class="xref py py-class docutils literal notranslate">HTMLParser</code></a> is
now <code class="docutils literal notranslate">True</code> by default. (Contributed by Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue21047">bpo-21047</a>.)</li>
<li>Although it is not formally part of the API, it is worth noting for porting
purposes (ie: fixing tests) that error messages that were previously of the
form “‘sometype’ does not support the buffer protocol” are now of the form “a
<a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a> is required, not ‘sometype’”.
(Contributed by Ezio Melotti in <a class="reference external" href="https://bugs.python.org/issue16518">bpo-16518</a>.)</li>
<li>If the current directory is set to a directory that no longer exists then
<a class="reference internal" href="../library/exceptions.html#FileNotFoundError" title="FileNotFoundError"><code class="xref py py-exc docutils literal notranslate">FileNotFoundError</code></a> will no longer be raised and instead
<a class="reference internal" href="../library/importlib.html#importlib.machinery.FileFinder.find_spec" title="importlib.machinery.FileFinder.find_spec"><code class="xref py py-meth docutils literal notranslate">find_spec()</code></a> will return <code class="docutils literal notranslate">None</code>
without caching <code class="docutils literal notranslate">None</code> in <a class="reference internal" href="../library/sys.html#sys.path_importer_cache" title="sys.path_importer_cache"><code class="xref py py-data docutils literal notranslate">sys.path_importer_cache</code></a>, which is
different than the typical case (<a class="reference external" href="https://bugs.python.org/issue22834">bpo-22834</a>).</li>
<li>HTTP status code and messages from <a class="reference internal" href="../library/http.client.html#module-http.client" title="http.client: HTTP and HTTPS protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">http.client</code></a> and <a class="reference internal" href="../library/http.server.html#module-http.server" title="http.server: HTTP server and request handlers."><code class="xref py py-mod docutils literal notranslate">http.server</code></a>
were refactored into a common <a class="reference internal" href="../library/http.html#http.HTTPStatus" title="http.HTTPStatus"><code class="xref py py-class docutils literal notranslate">HTTPStatus</code></a> enum. The values in
<a class="reference internal" href="../library/http.client.html#module-http.client" title="http.client: HTTP and HTTPS protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">http.client</code></a> and <a class="reference internal" href="../library/http.server.html#module-http.server" title="http.server: HTTP server and request handlers."><code class="xref py py-mod docutils literal notranslate">http.server</code></a> remain available for backwards
compatibility. (Contributed by Demian Brecht in <a class="reference external" href="https://bugs.python.org/issue21793">bpo-21793</a>.)</li>
<li>When an import loader defines <code class="xref py py-meth docutils literal notranslate">importlib.machinery.Loader.exec_module()</code>
it is now expected to also define
<code class="xref py py-meth docutils literal notranslate">create_module()</code> (raises a
<a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a> now, will be an error in Python 3.6). If the loader
inherits from <a class="reference internal" href="../library/importlib.html#importlib.abc.Loader" title="importlib.abc.Loader"><code class="xref py py-class docutils literal notranslate">importlib.abc.Loader</code></a> then there is nothing to do, else
simply define <code class="xref py py-meth docutils literal notranslate">create_module()</code> to return
<code class="docutils literal notranslate">None</code>. (Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue23014">bpo-23014</a>.)</li>
<li>The <a class="reference internal" href="../library/re.html#re.split" title="re.split"><code class="xref py py-func docutils literal notranslate">re.split()</code></a> function always ignored empty pattern matches, so the
<code class="docutils literal notranslate">&quot;x*&quot;</code> pattern worked the same as <code class="docutils literal notranslate">&quot;x+&quot;</code>, and the <code class="docutils literal notranslate">&quot;\b&quot;</code> pattern never
worked. Now <a class="reference internal" href="../library/re.html#re.split" title="re.split"><code class="xref py py-func docutils literal notranslate">re.split()</code></a> raises a warning if the pattern could match
an empty string. For compatibility, use patterns that never match an empty
string (e.g. <code class="docutils literal notranslate">&quot;x+&quot;</code> instead of <code class="docutils literal notranslate">&quot;x*&quot;</code>). Patterns that could only match
an empty string (such as <code class="docutils literal notranslate">&quot;\b&quot;</code>) now raise an error.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue22818">bpo-22818</a>.)</li>
<li>The <a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel" title="http.cookies.Morsel"><code class="xref py py-class docutils literal notranslate">http.cookies.Morsel</code></a> dict-like interface has been made self
consistent: morsel comparison now takes the <a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel.key" title="http.cookies.Morsel.key"><code class="xref py py-attr docutils literal notranslate">key</code></a>
and <a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel.value" title="http.cookies.Morsel.value"><code class="xref py py-attr docutils literal notranslate">value</code></a> into account,
<a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel.copy" title="http.cookies.Morsel.copy"><code class="xref py py-meth docutils literal notranslate">copy()</code></a> now results in a
<a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel" title="http.cookies.Morsel"><code class="xref py py-class docutils literal notranslate">Morsel</code></a> instance rather than a <a class="reference internal" href="../library/stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate">dict</code></a>, and
<a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel.update" title="http.cookies.Morsel.update"><code class="xref py py-meth docutils literal notranslate">update()</code></a> will now raise an exception if any of the
keys in the update dictionary are invalid. In addition, the undocumented
LegalChars parameter of <a class="reference internal" href="../library/http.cookies.html#http.cookies.Morsel.set" title="http.cookies.Morsel.set"><code class="xref py py-func docutils literal notranslate">set()</code></a> is deprecated and
is now ignored. (Contributed by Demian Brecht in <a class="reference external" href="https://bugs.python.org/issue2211">bpo-2211</a>.)</li>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0488">PEP 488</a> has removed <code class="docutils literal notranslate">.pyo</code> files from Python and introduced the optional
<code class="docutils literal notranslate">opt-</code> tag in <code class="docutils literal notranslate">.pyc</code> file names. The
<a class="reference internal" href="../library/importlib.html#importlib.util.cache_from_source" title="importlib.util.cache_from_source"><code class="xref py py-func docutils literal notranslate">importlib.util.cache_from_source()</code></a> has gained an optimization
parameter to help control the <code class="docutils literal notranslate">opt-</code> tag. Because of this, the
debug_override parameter of the function is now deprecated. <cite>.pyo</cite> files
are also no longer supported as a file argument to the Python interpreter and
thus serve no purpose when distributed on their own (i.e. sourceless code
distribution). Due to the fact that the magic number for bytecode has changed
in Python 3.5, all old <cite>.pyo</cite> files from previous versions of Python are
invalid regardless of this PEP.</li>
<li>The <a class="reference internal" href="../library/socket.html#module-socket" title="socket: Low-level networking interface."><code class="xref py py-mod docutils literal notranslate">socket</code></a> module now exports the <a class="reference internal" href="../library/socket.html#socket.CAN_RAW_FD_FRAMES" title="socket.CAN_RAW_FD_FRAMES"><code class="xref py py-data docutils literal notranslate">CAN_RAW_FD_FRAMES</code></a>
constant on linux 3.6 and greater.</li>
<li>The <a class="reference internal" href="../library/ssl.html#ssl.cert_time_to_seconds" title="ssl.cert_time_to_seconds"><code class="xref py py-func docutils literal notranslate">ssl.cert_time_to_seconds()</code></a> function now interprets the input time
as UTC and not as local time, per <a class="rfc reference external" href="https://tools.ietf.org/html/rfc5280.html">RFC 5280</a>. Additionally, the return
value is always an <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>. (Contributed by Akira Li in <a class="reference external" href="https://bugs.python.org/issue19940">bpo-19940</a>.)</li>
<li>The <code class="docutils literal notranslate">pygettext.py</code> Tool now uses the standard +NNNN format for timezones in
the POT-Creation-Date header.</li>
<li>The <a class="reference internal" href="../library/smtplib.html#module-smtplib" title="smtplib: SMTP protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">smtplib</code></a> module now uses <a class="reference internal" href="../library/sys.html#sys.stderr" title="sys.stderr"><code class="xref py py-data docutils literal notranslate">sys.stderr</code></a> instead of the previous
module-level <code class="xref py py-data docutils literal notranslate">stderr</code> variable for debug output. If your (test)
program depends on patching the module-level variable to capture the debug
output, you will need to update it to capture sys.stderr instead.</li>
<li>The <a class="reference internal" href="../library/stdtypes.html#str.startswith" title="str.startswith"><code class="xref py py-meth docutils literal notranslate">str.startswith()</code></a> and <a class="reference internal" href="../library/stdtypes.html#str.endswith" title="str.endswith"><code class="xref py py-meth docutils literal notranslate">str.endswith()</code></a> methods no longer return
<code class="docutils literal notranslate">True</code> when finding the empty string and the indexes are completely out of
range. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue24284">bpo-24284</a>.)</li>
<li>The <a class="reference internal" href="../library/inspect.html#inspect.getdoc" title="inspect.getdoc"><code class="xref py py-func docutils literal notranslate">inspect.getdoc()</code></a> function now returns documentation strings
inherited from base classes. Documentation strings no longer need to be
duplicated if the inherited documentation is appropriate. To suppress an
inherited string, an empty string must be specified (or the documentation
may be filled in). This change affects the output of the <a class="reference internal" href="../library/pydoc.html#module-pydoc" title="pydoc: Documentation generator and online help system."><code class="xref py py-mod docutils literal notranslate">pydoc</code></a>
module and the <a class="reference internal" href="../library/functions.html#help" title="help"><code class="xref py py-func docutils literal notranslate">help()</code></a> function.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue15582">bpo-15582</a>.)</li>
<li>Nested <a class="reference internal" href="../library/functools.html#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate">functools.partial()</code></a> calls are now flattened. If you were
relying on the previous behavior, you can now either add an attribute to a
<a class="reference internal" href="../library/functools.html#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate">functools.partial()</code></a> object or you can create a subclass of
<a class="reference internal" href="../library/functools.html#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate">functools.partial()</code></a>.
(Contributed by Alexander Belopolsky in <a class="reference external" href="https://bugs.python.org/issue7830">bpo-7830</a>.)</li>
</ul>
</div>
<div class="section" id="changes-in-the-c-api">
<h3>Changes in the C API<a class="headerlink" href="#changes-in-the-c-api" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li>The undocumented <code class="xref c c-member docutils literal notranslate">format</code> member of the
(non-public) <code class="xref c c-type docutils literal notranslate">PyMemoryViewObject</code> structure has been removed.
All extensions relying on the relevant parts in <code class="docutils literal notranslate">memoryobject.h</code>
must be rebuilt.</li>
<li>The <code class="xref c c-type docutils literal notranslate">PyMemAllocator</code> structure was renamed to
<a class="reference internal" href="../c-api/memory.html#c.PyMemAllocatorEx" title="PyMemAllocatorEx"><code class="xref c c-type docutils literal notranslate">PyMemAllocatorEx</code></a> and a new <code class="docutils literal notranslate">calloc</code> field was added.</li>
<li>Removed non-documented macro <code class="xref c c-macro docutils literal notranslate">PyObject_REPR</code> which leaked references.
Use format character <code class="docutils literal notranslate">%R</code> in <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FromFormat" title="PyUnicode_FromFormat"><code class="xref c c-func docutils literal notranslate">PyUnicode_FromFormat()</code></a>-like functions
to format the <a class="reference internal" href="../library/functions.html#repr" title="repr"><code class="xref py py-func docutils literal notranslate">repr()</code></a> of the object.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue22453">bpo-22453</a>.)</li>
<li>Because the lack of the <code class="xref py py-attr docutils literal notranslate">__module__</code> attribute breaks pickling and
introspection, a deprecation warning is now raised for builtin types without
the <code class="xref py py-attr docutils literal notranslate">__module__</code> attribute. This would be an AttributeError in
the future.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue20204">bpo-20204</a>.)</li>
<li>As part of the <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0492">PEP 492</a> implementation, the <code class="docutils literal notranslate">tp_reserved</code> slot of
<a class="reference internal" href="../c-api/type.html#c.PyTypeObject" title="PyTypeObject"><code class="xref c c-type docutils literal notranslate">PyTypeObject</code></a> was replaced with a
<a class="reference internal" href="../c-api/typeobj.html#c.tp_as_async" title="tp_as_async"><code class="xref c c-member docutils literal notranslate">tp_as_async</code></a> slot. Refer to <a class="reference internal" href="../c-api/coro.html#coro-objects">Coroutine Objects</a> for
new types, structures and functions.</li>
</ul>
</div>
</div>
<div class="section" id="notable-changes-in-python-3-5-4">
<h2>Notable changes in Python 3.5.4<a class="headerlink" href="#notable-changes-in-python-3-5-4" title="Permalink to this headline">¶</a></h2>
<div class="section" id="new-make-regen-all-build-target">
<h3>New <code class="docutils literal notranslate">make regen-all</code> build target<a class="headerlink" href="#new-make-regen-all-build-target" title="Permalink to this headline">¶</a></h3>
To simplify cross-compilation, and to ensure that CPython can reliably be
compiled without requiring an existing version of Python to already be
available, the autotools-based build system no longer attempts to implicitly
recompile generated files based on file modification times.
Instead, a new <code class="docutils literal notranslate">make regen-all</code> command has been added to force regeneration
of these files when desired (e.g. after an initial version of Python has
already been built based on the pregenerated versions).
More selective regeneration targets are also defined - see
<a class="reference external" href="https://github.com/python/cpython/tree/3.6/Makefile.pre.in">Makefile.pre.in</a> for details.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue23404">bpo-23404</a>.)
<div class="versionadded">
New in version 3.5.4.
</div>
</div>
<div class="section" id="removal-of-make-touch-build-target">
<h3>Removal of <code class="docutils literal notranslate">make touch</code> build target<a class="headerlink" href="#removal-of-make-touch-build-target" title="Permalink to this headline">¶</a></h3>
The <code class="docutils literal notranslate">make touch</code> build target previously used to request implicit regeneration
of generated files by updating their modification times has been removed.
It has been replaced by the new <code class="docutils literal notranslate">make regen-all</code> target.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue23404">bpo-23404</a>.)
<div class="versionchanged">
Changed in version 3.5.4.
</div>
</div>
</div>
</div>

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 <h3><a href="../contents.html">Table Of Contents</a></h3>
 <ul>
<li><a class="reference internal" href="#">What’s New In Python 3.5</a><ul>
<li><a class="reference internal" href="#summary-release-highlights">Summary – Release highlights</a></li>
<li><a class="reference internal" href="#new-features">New Features</a><ul>
<li><a class="reference internal" href="#pep-492-coroutines-with-async-and-await-syntax">PEP 492 - Coroutines with async and await syntax</a></li>
<li><a class="reference internal" href="#pep-465-a-dedicated-infix-operator-for-matrix-multiplication">PEP 465 - A dedicated infix operator for matrix multiplication</a></li>
<li><a class="reference internal" href="#pep-448-additional-unpacking-generalizations">PEP 448 - Additional Unpacking Generalizations</a></li>
<li><a class="reference internal" href="#pep-461-percent-formatting-support-for-bytes-and-bytearray">PEP 461 - percent formatting support for bytes and bytearray</a></li>
<li><a class="reference internal" href="#pep-484-type-hints">PEP 484 - Type Hints</a></li>
<li><a class="reference internal" href="#pep-471-os-scandir-function-a-better-and-faster-directory-iterator">PEP 471 - os.scandir() function – a better and faster directory iterator</a></li>
<li><a class="reference internal" href="#pep-475-retry-system-calls-failing-with-eintr">PEP 475: Retry system calls failing with EINTR</a></li>
<li><a class="reference internal" href="#pep-479-change-stopiteration-handling-inside-generators">PEP 479: Change StopIteration handling inside generators</a></li>
<li><a class="reference internal" href="#pep-485-a-function-for-testing-approximate-equality">PEP 485: A function for testing approximate equality</a></li>
<li><a class="reference internal" href="#pep-486-make-the-python-launcher-aware-of-virtual-environments">PEP 486: Make the Python Launcher aware of virtual environments</a></li>
<li><a class="reference internal" href="#pep-488-elimination-of-pyo-files">PEP 488: Elimination of PYO files</a></li>
<li><a class="reference internal" href="#pep-489-multi-phase-extension-module-initialization">PEP 489: Multi-phase extension module initialization</a></li>
</ul>
</li>
<li><a class="reference internal" href="#other-language-changes">Other Language Changes</a></li>
<li><a class="reference internal" href="#new-modules">New Modules</a><ul>
<li><a class="reference internal" href="#typing">typing</a></li>
<li><a class="reference internal" href="#zipapp">zipapp</a></li>
</ul>
</li>
<li><a class="reference internal" href="#improved-modules">Improved Modules</a><ul>
<li><a class="reference internal" href="#argparse">argparse</a></li>
<li><a class="reference internal" href="#asyncio">asyncio</a></li>
<li><a class="reference internal" href="#bz2">bz2</a></li>
<li><a class="reference internal" href="#cgi">cgi</a></li>
<li><a class="reference internal" href="#cmath">cmath</a></li>
<li><a class="reference internal" href="#code">code</a></li>
<li><a class="reference internal" href="#collections">collections</a></li>
<li><a class="reference internal" href="#collections-abc">collections.abc</a></li>
<li><a class="reference internal" href="#compileall">compileall</a></li>
<li><a class="reference internal" href="#concurrent-futures">concurrent.futures</a></li>
<li><a class="reference internal" href="#configparser">configparser</a></li>
<li><a class="reference internal" href="#contextlib">contextlib</a></li>
<li><a class="reference internal" href="#csv">csv</a></li>
<li><a class="reference internal" href="#curses">curses</a></li>
<li><a class="reference internal" href="#dbm">dbm</a></li>
<li><a class="reference internal" href="#difflib">difflib</a></li>
<li><a class="reference internal" href="#distutils">distutils</a></li>
<li><a class="reference internal" href="#doctest">doctest</a></li>
<li><a class="reference internal" href="#email">email</a></li>
<li><a class="reference internal" href="#enum">enum</a></li>
<li><a class="reference internal" href="#faulthandler">faulthandler</a></li>
<li><a class="reference internal" href="#functools">functools</a></li>
<li><a class="reference internal" href="#glob">glob</a></li>
<li><a class="reference internal" href="#gzip">gzip</a></li>
<li><a class="reference internal" href="#heapq">heapq</a></li>
<li><a class="reference internal" href="#http">http</a></li>
<li><a class="reference internal" href="#http-client">http.client</a></li>
<li><a class="reference internal" href="#idlelib-and-idle">idlelib and IDLE</a></li>
<li><a class="reference internal" href="#imaplib">imaplib</a></li>
<li><a class="reference internal" href="#imghdr">imghdr</a></li>
<li><a class="reference internal" href="#importlib">importlib</a></li>
<li><a class="reference internal" href="#inspect">inspect</a></li>
<li><a class="reference internal" href="#io">io</a></li>
<li><a class="reference internal" href="#ipaddress">ipaddress</a></li>
<li><a class="reference internal" href="#json">json</a></li>
<li><a class="reference internal" href="#linecache">linecache</a></li>
<li><a class="reference internal" href="#locale">locale</a></li>
<li><a class="reference internal" href="#logging">logging</a></li>
<li><a class="reference internal" href="#lzma">lzma</a></li>
<li><a class="reference internal" href="#math">math</a></li>
<li><a class="reference internal" href="#multiprocessing">multiprocessing</a></li>
<li><a class="reference internal" href="#operator">operator</a></li>
<li><a class="reference internal" href="#os">os</a></li>
<li><a class="reference internal" href="#pathlib">pathlib</a></li>
<li><a class="reference internal" href="#pickle">pickle</a></li>
<li><a class="reference internal" href="#poplib">poplib</a></li>
<li><a class="reference internal" href="#re">re</a></li>
<li><a class="reference internal" href="#readline">readline</a></li>
<li><a class="reference internal" href="#selectors">selectors</a></li>
<li><a class="reference internal" href="#shutil">shutil</a></li>
<li><a class="reference internal" href="#signal">signal</a></li>
<li><a class="reference internal" href="#smtpd">smtpd</a></li>
<li><a class="reference internal" href="#smtplib">smtplib</a></li>
<li><a class="reference internal" href="#sndhdr">sndhdr</a></li>
<li><a class="reference internal" href="#socket">socket</a></li>
<li><a class="reference internal" href="#ssl">ssl</a><ul>
<li><a class="reference internal" href="#memory-bio-support">Memory BIO Support</a></li>
<li><a class="reference internal" href="#application-layer-protocol-negotiation-support">Application-Layer Protocol Negotiation Support</a></li>
<li><a class="reference internal" href="#other-changes">Other Changes</a></li>
</ul>
</li>
<li><a class="reference internal" href="#sqlite3">sqlite3</a></li>
<li><a class="reference internal" href="#subprocess">subprocess</a></li>
<li><a class="reference internal" href="#sys">sys</a></li>
<li><a class="reference internal" href="#sysconfig">sysconfig</a></li>
<li><a class="reference internal" href="#tarfile">tarfile</a></li>
<li><a class="reference internal" href="#threading">threading</a></li>
<li><a class="reference internal" href="#time">time</a></li>
<li><a class="reference internal" href="#timeit">timeit</a></li>
<li><a class="reference internal" href="#tkinter">tkinter</a></li>
<li><a class="reference internal" href="#traceback">traceback</a></li>
<li><a class="reference internal" href="#types">types</a></li>
<li><a class="reference internal" href="#unicodedata">unicodedata</a></li>
<li><a class="reference internal" href="#unittest">unittest</a></li>
<li><a class="reference internal" href="#unittest-mock">unittest.mock</a></li>
<li><a class="reference internal" href="#urllib">urllib</a></li>
<li><a class="reference internal" href="#wsgiref">wsgiref</a></li>
<li><a class="reference internal" href="#xmlrpc">xmlrpc</a></li>
<li><a class="reference internal" href="#xml-sax">xml.sax</a></li>
<li><a class="reference internal" href="#zipfile">zipfile</a></li>
</ul>
</li>
<li><a class="reference internal" href="#other-module-level-changes">Other module-level changes</a></li>
<li><a class="reference internal" href="#optimizations">Optimizations</a></li>
<li><a class="reference internal" href="#build-and-c-api-changes">Build and C API Changes</a></li>
<li><a class="reference internal" href="#deprecated">Deprecated</a><ul>
<li><a class="reference internal" href="#new-keywords">New Keywords</a></li>
<li><a class="reference internal" href="#deprecated-python-behavior">Deprecated Python Behavior</a></li>
<li><a class="reference internal" href="#unsupported-operating-systems">Unsupported Operating Systems</a></li>
<li><a class="reference internal" href="#deprecated-python-modules-functions-and-methods">Deprecated Python modules, functions and methods</a></li>
</ul>
</li>
<li><a class="reference internal" href="#removed">Removed</a><ul>
<li><a class="reference internal" href="#api-and-feature-removals">API and Feature Removals</a></li>
</ul>
</li>
<li><a class="reference internal" href="#porting-to-python-3-5">Porting to Python 3.5</a><ul>
<li><a class="reference internal" href="#changes-in-python-behavior">Changes in Python behavior</a></li>
<li><a class="reference internal" href="#changes-in-the-python-api">Changes in the Python API</a></li>
<li><a class="reference internal" href="#changes-in-the-c-api">Changes in the C API</a></li>
</ul>
</li>
<li><a class="reference internal" href="#notable-changes-in-python-3-5-4">Notable changes in Python 3.5.4</a><ul>
<li><a class="reference internal" href="#new-make-regen-all-build-target">New <code class="docutils literal notranslate">make regen-all</code> build target</a></li>
<li><a class="reference internal" href="#removal-of-make-touch-build-target">Removal of <code class="docutils literal notranslate">make touch</code> build target</a></li>
</ul>
</li>
</ul>
</li>
</ul>

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