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 <div class="section" id="module-doctest">
<h1>26.3. <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> — Test interactive Python examples<a class="headerlink" href="#module-doctest" title="Permalink to this headline">¶</a></h1>
Source code: <a class="reference external" href="https://github.com/python/cpython/tree/3.6/Lib/doctest.py">Lib/doctest.py</a>
<hr class="docutils" />
The <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> module searches for pieces of text that look like interactive
Python sessions, and then executes those sessions to verify that they work
exactly as shown. There are several common ways to use doctest:
<ul class="simple">
<li>To check that a module’s docstrings are up-to-date by verifying that all
interactive examples still work as documented.</li>
<li>To perform regression testing by verifying that interactive examples from a
test file or a test object work as expected.</li>
<li>To write tutorial documentation for a package, liberally illustrated with
input-output examples. Depending on whether the examples or the expository text
are emphasized, this has the flavor of “literate testing” or “executable
documentation”.</li>
</ul>
Here’s a complete but small example module:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&quot;&quot;&quot;
This is the &quot;example&quot; module.

The example module supplies one function, factorial(). For example,

&gt;&gt;&gt; factorial(5)
120
&quot;&quot;&quot;

def factorial(n):
 &quot;&quot;&quot;Return the factorial of n, an exact integer &gt;= 0.

&gt;&gt;&gt; [factorial(n) for n in range(6)]
 [1, 1, 2, 6, 24, 120]
 &gt;&gt;&gt; factorial(30)
 265252859812191058636308480000000
 &gt;&gt;&gt; factorial(-1)
 Traceback (most recent call last):
 ...
 ValueError: n must be &gt;= 0

Factorials of floats are OK, but the float must be an exact integer:
 &gt;&gt;&gt; factorial(30.1)
 Traceback (most recent call last):
 ...
 ValueError: n must be exact integer
 &gt;&gt;&gt; factorial(30.0)
 265252859812191058636308480000000

It must also not be ridiculously large:
 &gt;&gt;&gt; factorial(1e100)
 Traceback (most recent call last):
 ...
 OverflowError: n too large
 &quot;&quot;&quot;

import math
 if not n &gt;= 0:
 raise ValueError(&quot;n must be &gt;= 0&quot;)
 if math.floor(n) != n:
 raise ValueError(&quot;n must be exact integer&quot;)
 if n+1 == n: # catch a value like 1e300
 raise OverflowError(&quot;n too large&quot;)
 result = 1
 factor = 2
 while factor &lt;= n:
 result *= factor
 factor += 1
 return result

if __name__ == &quot;__main__&quot;:
 import doctest
 doctest.testmod()
</pre></div>
</div>
If you run <code class="file docutils literal notranslate">example.py</code> directly from the command line, <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a>
works its magic:
<div class="highlight-shell-session notranslate"><div class="highlight"><pre>$ python example.py
$
</pre></div>
</div>
There’s no output! That’s normal, and it means all the examples worked. Pass
<code class="docutils literal notranslate">-v</code> to the script, and <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> prints a detailed log of what
it’s trying, and prints a summary at the end:
<div class="highlight-shell-session notranslate"><div class="highlight"><pre>$ python example.py -v
Trying:
 factorial(5)
Expecting:
 120
ok
Trying:
 [factorial(n) for n in range(6)]
Expecting:
 [1, 1, 2, 6, 24, 120]
ok
</pre></div>
</div>
And so on, eventually ending with:
<div class="highlight-none notranslate"><div class="highlight"><pre>Trying:
 factorial(1e100)
Expecting:
 Traceback (most recent call last):
 ...
 OverflowError: n too large
ok
2 items passed all tests:
 1 tests in __main__
 8 tests in __main__.factorial
9 tests in 2 items.
9 passed and 0 failed.
Test passed.
$
</pre></div>
</div>
That’s all you need to know to start making productive use of <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a>!
Jump in. The following sections provide full details. Note that there are many
examples of doctests in the standard Python test suite and libraries.
Especially useful examples can be found in the standard test file
<code class="file docutils literal notranslate">Lib/test/test_doctest.py</code>.
<div class="section" id="simple-usage-checking-examples-in-docstrings">
<h2>26.3.1. Simple Usage: Checking Examples in Docstrings<a class="headerlink" href="#simple-usage-checking-examples-in-docstrings" title="Permalink to this headline">¶</a></h2>
The simplest way to start using doctest (but not necessarily the way you’ll
continue to do it) is to end each module <code class="xref py py-mod docutils literal notranslate">M</code> with:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>if __name__ == &quot;__main__&quot;:
 import doctest
 doctest.testmod()
</pre></div>
</div>
<a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> then examines docstrings in module <code class="xref py py-mod docutils literal notranslate">M</code>.
Running the module as a script causes the examples in the docstrings to get
executed and verified:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>python M.py
</pre></div>
</div>
This won’t display anything unless an example fails, in which case the failing
example(s) and the cause(s) of the failure(s) are printed to stdout, and the
final line of output is <code class="docutils literal notranslate">***Test Failed*** N failures.</code>, where N is the
number of examples that failed.
Run it with the <code class="docutils literal notranslate">-v</code> switch instead:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>python M.py -v
</pre></div>
</div>
and a detailed report of all examples tried is printed to standard output, along
with assorted summaries at the end.
You can force verbose mode by passing <code class="docutils literal notranslate">verbose=True</code> to <a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a>, or
prohibit it by passing <code class="docutils literal notranslate">verbose=False</code>. In either of those cases,
<code class="docutils literal notranslate">sys.argv</code> is not examined by <a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a> (so passing <code class="docutils literal notranslate">-v</code> or not
has no effect).
There is also a command line shortcut for running <a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a>. You can
instruct the Python interpreter to run the doctest module directly from the
standard library and pass the module name(s) on the command line:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>python -m doctest -v example.py
</pre></div>
</div>
This will import <code class="file docutils literal notranslate">example.py</code> as a standalone module and run
<a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a> on it. Note that this may not work correctly if the file is
part of a package and imports other submodules from that package.
For more information on <a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a>, see section <a class="reference internal" href="#doctest-basic-api">Basic API</a>.
</div>
<div class="section" id="simple-usage-checking-examples-in-a-text-file">
<h2>26.3.2. Simple Usage: Checking Examples in a Text File<a class="headerlink" href="#simple-usage-checking-examples-in-a-text-file" title="Permalink to this headline">¶</a></h2>
Another simple application of doctest is testing interactive examples in a text
file. This can be done with the <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a> function:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>import doctest
doctest.testfile(&quot;example.txt&quot;)
</pre></div>
</div>
That short script executes and verifies any interactive Python examples
contained in the file <code class="file docutils literal notranslate">example.txt</code>. The file content is treated as if it
were a single giant docstring; the file doesn’t need to contain a Python
program! For example, perhaps <code class="file docutils literal notranslate">example.txt</code> contains this:
<div class="highlight-none notranslate"><div class="highlight"><pre>The ``example`` module
======================

Using ``factorial``
-------------------

This is an example text file in reStructuredText format.  First import
``factorial`` from the ``example`` module:

&gt;&gt;&gt; from example import factorial

Now use it:

&gt;&gt;&gt; factorial(6)
 120
</pre></div>
</div>
Running <code class="docutils literal notranslate">doctest.testfile(&quot;example.txt&quot;)</code> then finds the error in this
documentation:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>File &quot;./example.txt&quot;, line 14, in example.txt
Failed example:
 factorial(6)
Expected:
 120
Got:
 720
</pre></div>
</div>
As with <a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a>, <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a> won’t display anything unless an
example fails. If an example does fail, then the failing example(s) and the
cause(s) of the failure(s) are printed to stdout, using the same format as
<a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a>.
By default, <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a> looks for files in the calling module’s directory.
See section <a class="reference internal" href="#doctest-basic-api">Basic API</a> for a description of the optional arguments
that can be used to tell it to look for files in other locations.
Like <a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a>, <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a>’s verbosity can be set with the
<code class="docutils literal notranslate">-v</code> command-line switch or with the optional keyword argument
verbose.
There is also a command line shortcut for running <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a>. You can
instruct the Python interpreter to run the doctest module directly from the
standard library and pass the file name(s) on the command line:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>python -m doctest -v example.txt
</pre></div>
</div>
Because the file name does not end with <code class="file docutils literal notranslate">.py</code>, <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> infers that
it must be run with <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a>, not <a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a>.
For more information on <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a>, see section <a class="reference internal" href="#doctest-basic-api">Basic API</a>.
</div>
<div class="section" id="how-it-works">
<h2>26.3.3. How It Works<a class="headerlink" href="#how-it-works" title="Permalink to this headline">¶</a></h2>
This section examines in detail how doctest works: which docstrings it looks at,
how it finds interactive examples, what execution context it uses, how it
handles exceptions, and how option flags can be used to control its behavior.
This is the information that you need to know to write doctest examples; for
information about actually running doctest on these examples, see the following
sections.
<div class="section" id="which-docstrings-are-examined">
<h3>26.3.3.1. Which Docstrings Are Examined?<a class="headerlink" href="#which-docstrings-are-examined" title="Permalink to this headline">¶</a></h3>
The module docstring, and all function, class and method docstrings are
searched. Objects imported into the module are not searched.
In addition, if <code class="docutils literal notranslate">M.__test__</code> exists and “is true”, it must be a dict, and each
entry maps a (string) name to a function object, class object, or string.
Function and class object docstrings found from <code class="docutils literal notranslate">M.__test__</code> are searched, and
strings are treated as if they were docstrings. In output, a key <code class="docutils literal notranslate">K</code> in
<code class="docutils literal notranslate">M.__test__</code> appears with name
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&lt;name of M&gt;.__test__.K
</pre></div>
</div>
Any classes found are recursively searched similarly, to test docstrings in
their contained methods and nested classes.
<div class="impl-detail compound">
CPython implementation detail: Prior to version 3.4, extension modules written in C were not fully
searched by doctest.
</div>
</div>
<div class="section" id="how-are-docstring-examples-recognized">
<h3>26.3.3.2. How are Docstring Examples Recognized?<a class="headerlink" href="#how-are-docstring-examples-recognized" title="Permalink to this headline">¶</a></h3>
In most cases a copy-and-paste of an interactive console session works fine,
but doctest isn’t trying to do an exact emulation of any specific Python shell.
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; # comments are ignored
&gt;&gt;&gt; x = 12
&gt;&gt;&gt; x
12
&gt;&gt;&gt; if x == 13:
... print(&quot;yes&quot;)
... else:
... print(&quot;no&quot;)
... print(&quot;NO&quot;)
... print(&quot;NO!!!&quot;)
...
no
NO
NO!!!
&gt;&gt;&gt;
</pre></div>
</div>
Any expected output must immediately follow the final <code class="docutils literal notranslate">'&gt;&gt;&gt; '</code> or <code class="docutils literal notranslate">'... '</code>
line containing the code, and the expected output (if any) extends to the next
<code class="docutils literal notranslate">'&gt;&gt;&gt; '</code> or all-whitespace line.
The fine print:
<ul>
<li>Expected output cannot contain an all-whitespace line, since such a line is
taken to signal the end of expected output. If expected output does contain a
blank line, put <code class="docutils literal notranslate">&lt;BLANKLINE&gt;</code> in your doctest example each place a blank line
is expected.
</li>
<li>All hard tab characters are expanded to spaces, using 8-column tab stops.
Tabs in output generated by the tested code are not modified. Because any
hard tabs in the sample output are expanded, this means that if the code
output includes hard tabs, the only way the doctest can pass is if the
<a class="reference internal" href="#doctest.NORMALIZE_WHITESPACE" title="doctest.NORMALIZE_WHITESPACE"><code class="xref py py-const docutils literal notranslate">NORMALIZE_WHITESPACE</code></a> option or <a class="reference internal" href="#doctest-directives">directive</a>
is in effect.
Alternatively, the test can be rewritten to capture the output and compare it
to an expected value as part of the test. This handling of tabs in the
source was arrived at through trial and error, and has proven to be the least
error prone way of handling them. It is possible to use a different
algorithm for handling tabs by writing a custom <a class="reference internal" href="#doctest.DocTestParser" title="doctest.DocTestParser"><code class="xref py py-class docutils literal notranslate">DocTestParser</code></a> class.
</li>
<li>Output to stdout is captured, but not output to stderr (exception tracebacks
are captured via a different means).
</li>
<li>If you continue a line via backslashing in an interactive session, or for any
other reason use a backslash, you should use a raw docstring, which will
preserve your backslashes exactly as you type them:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; def f(x):
... r&#39;&#39;&#39;Backslashes in a raw docstring: m\n&#39;&#39;&#39;
&gt;&gt;&gt; print(f.__doc__)
Backslashes in a raw docstring: m\n
</pre></div>
</div>
Otherwise, the backslash will be interpreted as part of the string. For example,
the <code class="docutils literal notranslate">\n</code> above would be interpreted as a newline character. Alternatively, you
can double each backslash in the doctest version (and not use a raw string):
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; def f(x):
... &#39;&#39;&#39;Backslashes in a raw docstring: m\\n&#39;&#39;&#39;
&gt;&gt;&gt; print(f.__doc__)
Backslashes in a raw docstring: m\n
</pre></div>
</div>
</li>
<li>The starting column doesn’t matter:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; assert &quot;Easy!&quot;
 &gt;&gt;&gt; import math
 &gt;&gt;&gt; math.floor(1.9)
 1
</pre></div>
</div>
and as many leading whitespace characters are stripped from the expected output
as appeared in the initial <code class="docutils literal notranslate">'&gt;&gt;&gt; '</code> line that started the example.
</li>
</ul>
</div>
<div class="section" id="what-s-the-execution-context">
<h3>26.3.3.3. What’s the Execution Context?<a class="headerlink" href="#what-s-the-execution-context" title="Permalink to this headline">¶</a></h3>
By default, each time <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> finds a docstring to test, it uses a
shallow copy of <code class="xref py py-mod docutils literal notranslate">M</code>’s globals, so that running tests doesn’t change the
module’s real globals, and so that one test in <code class="xref py py-mod docutils literal notranslate">M</code> can’t leave behind
crumbs that accidentally allow another test to work. This means examples can
freely use any names defined at top-level in <code class="xref py py-mod docutils literal notranslate">M</code>, and names defined earlier
in the docstring being run. Examples cannot see names defined in other
docstrings.
You can force use of your own dict as the execution context by passing
<code class="docutils literal notranslate">globs=your_dict</code> to <a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a> or <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a> instead.
</div>
<div class="section" id="what-about-exceptions">
<h3>26.3.3.4. What About Exceptions?<a class="headerlink" href="#what-about-exceptions" title="Permalink to this headline">¶</a></h3>
No problem, provided that the traceback is the only output produced by the
example: just paste in the traceback. <a class="footnote-reference" href="#id2" id="id1">[1]</a> Since tracebacks contain details
that are likely to change rapidly (for example, exact file paths and line
numbers), this is one case where doctest works hard to be flexible in what it
accepts.
Simple example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; [1, 2, 3].remove(42)
Traceback (most recent call last):
 File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
ValueError: list.remove(x): x not in list
</pre></div>
</div>
That doctest succeeds if <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> is raised, with the <code class="docutils literal notranslate">list.remove(x):
x not in list</code> detail as shown.
The expected output for an exception must start with a traceback header, which
may be either of the following two lines, indented the same as the first line of
the example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Traceback (most recent call last):
Traceback (innermost last):
</pre></div>
</div>
The traceback header is followed by an optional traceback stack, whose contents
are ignored by doctest. The traceback stack is typically omitted, or copied
verbatim from an interactive session.
The traceback stack is followed by the most interesting part: the line(s)
containing the exception type and detail. This is usually the last line of a
traceback, but can extend across multiple lines if the exception has a
multi-line detail:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; raise ValueError(&#39;multi\n line\ndetail&#39;)
Traceback (most recent call last):
 File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
ValueError: multi
 line
detail
</pre></div>
</div>
The last three lines (starting with <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a>) are compared against the
exception’s type and detail, and the rest are ignored.
Best practice is to omit the traceback stack, unless it adds significant
documentation value to the example. So the last example is probably better as:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; raise ValueError(&#39;multi\n line\ndetail&#39;)
Traceback (most recent call last):
 ...
ValueError: multi
 line
detail
</pre></div>
</div>
Note that tracebacks are treated very specially. In particular, in the
rewritten example, the use of <code class="docutils literal notranslate">...</code> is independent of doctest’s
<a class="reference internal" href="#doctest.ELLIPSIS" title="doctest.ELLIPSIS"><code class="xref py py-const docutils literal notranslate">ELLIPSIS</code></a> option. The ellipsis in that example could be left out, or
could just as well be three (or three hundred) commas or digits, or an indented
transcript of a Monty Python skit.
Some details you should read once, but won’t need to remember:
<ul>
<li>Doctest can’t guess whether your expected output came from an exception
traceback or from ordinary printing. So, e.g., an example that expects
<code class="docutils literal notranslate">ValueError: 42 is prime</code> will pass whether <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> is actually
raised or if the example merely prints that traceback text. In practice,
ordinary output rarely begins with a traceback header line, so this doesn’t
create real problems.
</li>
<li>Each line of the traceback stack (if present) must be indented further than
the first line of the example, or start with a non-alphanumeric character.
The first line following the traceback header indented the same and starting
with an alphanumeric is taken to be the start of the exception detail. Of
course this does the right thing for genuine tracebacks.
</li>
<li>When the <a class="reference internal" href="#doctest.IGNORE_EXCEPTION_DETAIL" title="doctest.IGNORE_EXCEPTION_DETAIL"><code class="xref py py-const docutils literal notranslate">IGNORE_EXCEPTION_DETAIL</code></a> doctest option is specified,
everything following the leftmost colon and any module information in the
exception name is ignored.
</li>
<li>The interactive shell omits the traceback header line for some
<a class="reference internal" href="exceptions.html#SyntaxError" title="SyntaxError"><code class="xref py py-exc docutils literal notranslate">SyntaxError</code></a>s. But doctest uses the traceback header line to
distinguish exceptions from non-exceptions. So in the rare case where you need
to test a <a class="reference internal" href="exceptions.html#SyntaxError" title="SyntaxError"><code class="xref py py-exc docutils literal notranslate">SyntaxError</code></a> that omits the traceback header, you will need to
manually add the traceback header line to your test example.
</li>
<li>For some <a class="reference internal" href="exceptions.html#SyntaxError" title="SyntaxError"><code class="xref py py-exc docutils literal notranslate">SyntaxError</code></a>s, Python displays the character position of the
syntax error, using a <code class="docutils literal notranslate">^</code> marker:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; 1 1
 File &quot;&lt;stdin&gt;&quot;, line 1
 1 1
 ^
SyntaxError: invalid syntax
</pre></div>
</div>
Since the lines showing the position of the error come before the exception type
and detail, they are not checked by doctest. For example, the following test
would pass, even though it puts the <code class="docutils literal notranslate">^</code> marker in the wrong location:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; 1 1
 File &quot;&lt;stdin&gt;&quot;, line 1
 1 1
 ^
SyntaxError: invalid syntax
</pre></div>
</div>
</li>
</ul>
</div>
<div class="section" id="option-flags">
<h3>26.3.3.5. Option Flags<a class="headerlink" href="#option-flags" title="Permalink to this headline">¶</a></h3>
A number of option flags control various aspects of doctest’s behavior.
Symbolic names for the flags are supplied as module constants, which can be
<a class="reference internal" href="../reference/expressions.html#bitwise">bitwise ORed</a> together and passed to various functions.
The names can also be used in <a class="reference internal" href="#doctest-directives">doctest directives</a>,
and may be passed to the doctest command line interface via the <code class="docutils literal notranslate">-o</code> option.
<div class="versionadded">
New in version 3.4: The <code class="docutils literal notranslate">-o</code> command line option.
</div>
The first group of options define test semantics, controlling aspects of how
doctest decides whether actual output matches an example’s expected output:
<dl class="data">
<dt id="doctest.DONT_ACCEPT_TRUE_FOR_1">
<code class="descclassname">doctest.</code><code class="descname">DONT_ACCEPT_TRUE_FOR_1</code><a class="headerlink" href="#doctest.DONT_ACCEPT_TRUE_FOR_1" title="Permalink to this definition">¶</a></dt>
<dd>By default, if an expected output block contains just <code class="docutils literal notranslate">1</code>, an actual output
block containing just <code class="docutils literal notranslate">1</code> or just <code class="docutils literal notranslate">True</code> is considered to be a match, and
similarly for <code class="docutils literal notranslate">0</code> versus <code class="docutils literal notranslate">False</code>. When <a class="reference internal" href="#doctest.DONT_ACCEPT_TRUE_FOR_1" title="doctest.DONT_ACCEPT_TRUE_FOR_1"><code class="xref py py-const docutils literal notranslate">DONT_ACCEPT_TRUE_FOR_1</code></a> is
specified, neither substitution is allowed. The default behavior caters to that
Python changed the return type of many functions from integer to boolean;
doctests expecting “little integer” output still work in these cases. This
option will probably go away, but not for several years.
</dd></dl>

<dl class="data">
<dt id="doctest.DONT_ACCEPT_BLANKLINE">
<code class="descclassname">doctest.</code><code class="descname">DONT_ACCEPT_BLANKLINE</code><a class="headerlink" href="#doctest.DONT_ACCEPT_BLANKLINE" title="Permalink to this definition">¶</a></dt>
<dd>By default, if an expected output block contains a line containing only the
string <code class="docutils literal notranslate">&lt;BLANKLINE&gt;</code>, then that line will match a blank line in the actual
output. Because a genuinely blank line delimits the expected output, this is
the only way to communicate that a blank line is expected. When
<a class="reference internal" href="#doctest.DONT_ACCEPT_BLANKLINE" title="doctest.DONT_ACCEPT_BLANKLINE"><code class="xref py py-const docutils literal notranslate">DONT_ACCEPT_BLANKLINE</code></a> is specified, this substitution is not allowed.
</dd></dl>

<dl class="data">
<dt id="doctest.NORMALIZE_WHITESPACE">
<code class="descclassname">doctest.</code><code class="descname">NORMALIZE_WHITESPACE</code><a class="headerlink" href="#doctest.NORMALIZE_WHITESPACE" title="Permalink to this definition">¶</a></dt>
<dd>When specified, all sequences of whitespace (blanks and newlines) are treated as
equal. Any sequence of whitespace within the expected output will match any
sequence of whitespace within the actual output. By default, whitespace must
match exactly. <a class="reference internal" href="#doctest.NORMALIZE_WHITESPACE" title="doctest.NORMALIZE_WHITESPACE"><code class="xref py py-const docutils literal notranslate">NORMALIZE_WHITESPACE</code></a> is especially useful when a line of
expected output is very long, and you want to wrap it across multiple lines in
your source.
</dd></dl>

<dl class="data">
<dt id="doctest.ELLIPSIS">
<code class="descclassname">doctest.</code><code class="descname">ELLIPSIS</code><a class="headerlink" href="#doctest.ELLIPSIS" title="Permalink to this definition">¶</a></dt>
<dd>When specified, an ellipsis marker (<code class="docutils literal notranslate">...</code>) in the expected output can match
any substring in the actual output. This includes substrings that span line
boundaries, and empty substrings, so it’s best to keep usage of this simple.
Complicated uses can lead to the same kinds of “oops, it matched too much!”
surprises that <code class="docutils literal notranslate">.*</code> is prone to in regular expressions.
</dd></dl>

<dl class="data">
<dt id="doctest.IGNORE_EXCEPTION_DETAIL">
<code class="descclassname">doctest.</code><code class="descname">IGNORE_EXCEPTION_DETAIL</code><a class="headerlink" href="#doctest.IGNORE_EXCEPTION_DETAIL" title="Permalink to this definition">¶</a></dt>
<dd>When specified, an example that expects an exception passes if an exception of
the expected type is raised, even if the exception detail does not match. For
example, an example expecting <code class="docutils literal notranslate">ValueError: 42</code> will pass if the actual
exception raised is <code class="docutils literal notranslate">ValueError: 3*14</code>, but will fail, e.g., if
<a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> is raised.
It will also ignore the module name used in Python 3 doctest reports. Hence
both of these variations will work with the flag specified, regardless of
whether the test is run under Python 2.7 or Python 3.2 (or later versions):
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; raise CustomError(&#39;message&#39;)
Traceback (most recent call last):
CustomError: message

&gt;&gt;&gt; raise CustomError(&#39;message&#39;)
Traceback (most recent call last):
my_module.CustomError: message
</pre></div>
</div>
Note that <a class="reference internal" href="#doctest.ELLIPSIS" title="doctest.ELLIPSIS"><code class="xref py py-const docutils literal notranslate">ELLIPSIS</code></a> can also be used to ignore the
details of the exception message, but such a test may still fail based
on whether or not the module details are printed as part of the
exception name. Using <a class="reference internal" href="#doctest.IGNORE_EXCEPTION_DETAIL" title="doctest.IGNORE_EXCEPTION_DETAIL"><code class="xref py py-const docutils literal notranslate">IGNORE_EXCEPTION_DETAIL</code></a> and the details
from Python 2.3 is also the only clear way to write a doctest that doesn’t
care about the exception detail yet continues to pass under Python 2.3 or
earlier (those releases do not support <a class="reference internal" href="#doctest-directives">doctest directives</a> and ignore them as irrelevant comments). For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; (1, 2)[3] = &#39;moo&#39;
Traceback (most recent call last):
 File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
TypeError: object doesn&#39;t support item assignment
</pre></div>
</div>
passes under Python 2.3 and later Python versions with the flag specified,
even though the detail
changed in Python 2.4 to say “does not” instead of “doesn’t”.
<div class="versionchanged">
Changed in version 3.2: <a class="reference internal" href="#doctest.IGNORE_EXCEPTION_DETAIL" title="doctest.IGNORE_EXCEPTION_DETAIL"><code class="xref py py-const docutils literal notranslate">IGNORE_EXCEPTION_DETAIL</code></a> now also ignores any information relating
to the module containing the exception under test.
</div>
</dd></dl>

<dl class="data">
<dt id="doctest.SKIP">
<code class="descclassname">doctest.</code><code class="descname">SKIP</code><a class="headerlink" href="#doctest.SKIP" title="Permalink to this definition">¶</a></dt>
<dd>When specified, do not run the example at all. This can be useful in contexts
where doctest examples serve as both documentation and test cases, and an
example should be included for documentation purposes, but should not be
checked. E.g., the example’s output might be random; or the example might
depend on resources which would be unavailable to the test driver.
The SKIP flag can also be used for temporarily “commenting out” examples.
</dd></dl>

<dl class="data">
<dt id="doctest.COMPARISON_FLAGS">
<code class="descclassname">doctest.</code><code class="descname">COMPARISON_FLAGS</code><a class="headerlink" href="#doctest.COMPARISON_FLAGS" title="Permalink to this definition">¶</a></dt>
<dd>A bitmask or’ing together all the comparison flags above.
</dd></dl>

The second group of options controls how test failures are reported:
<dl class="data">
<dt id="doctest.REPORT_UDIFF">
<code class="descclassname">doctest.</code><code class="descname">REPORT_UDIFF</code><a class="headerlink" href="#doctest.REPORT_UDIFF" title="Permalink to this definition">¶</a></dt>
<dd>When specified, failures that involve multi-line expected and actual outputs are
displayed using a unified diff.
</dd></dl>

<dl class="data">
<dt id="doctest.REPORT_CDIFF">
<code class="descclassname">doctest.</code><code class="descname">REPORT_CDIFF</code><a class="headerlink" href="#doctest.REPORT_CDIFF" title="Permalink to this definition">¶</a></dt>
<dd>When specified, failures that involve multi-line expected and actual outputs
will be displayed using a context diff.
</dd></dl>

<dl class="data">
<dt id="doctest.REPORT_NDIFF">
<code class="descclassname">doctest.</code><code class="descname">REPORT_NDIFF</code><a class="headerlink" href="#doctest.REPORT_NDIFF" title="Permalink to this definition">¶</a></dt>
<dd>When specified, differences are computed by <code class="docutils literal notranslate">difflib.Differ</code>, using the same
algorithm as the popular <code class="file docutils literal notranslate">ndiff.py</code> utility. This is the only method that
marks differences within lines as well as across lines. For example, if a line
of expected output contains digit <code class="docutils literal notranslate">1</code> where actual output contains letter
<code class="docutils literal notranslate">l</code>, a line is inserted with a caret marking the mismatching column positions.
</dd></dl>

<dl class="data">
<dt id="doctest.REPORT_ONLY_FIRST_FAILURE">
<code class="descclassname">doctest.</code><code class="descname">REPORT_ONLY_FIRST_FAILURE</code><a class="headerlink" href="#doctest.REPORT_ONLY_FIRST_FAILURE" title="Permalink to this definition">¶</a></dt>
<dd>When specified, display the first failing example in each doctest, but suppress
output for all remaining examples. This will prevent doctest from reporting
correct examples that break because of earlier failures; but it might also hide
incorrect examples that fail independently of the first failure. When
<a class="reference internal" href="#doctest.REPORT_ONLY_FIRST_FAILURE" title="doctest.REPORT_ONLY_FIRST_FAILURE"><code class="xref py py-const docutils literal notranslate">REPORT_ONLY_FIRST_FAILURE</code></a> is specified, the remaining examples are
still run, and still count towards the total number of failures reported; only
the output is suppressed.
</dd></dl>

<dl class="data">
<dt id="doctest.FAIL_FAST">
<code class="descclassname">doctest.</code><code class="descname">FAIL_FAST</code><a class="headerlink" href="#doctest.FAIL_FAST" title="Permalink to this definition">¶</a></dt>
<dd>When specified, exit after the first failing example and don’t attempt to run
the remaining examples. Thus, the number of failures reported will be at most
1. This flag may be useful during debugging, since examples after the first
failure won’t even produce debugging output.
The doctest command line accepts the option <code class="docutils literal notranslate">-f</code> as a shorthand for <code class="docutils literal notranslate">-o
FAIL_FAST</code>.
<div class="versionadded">
New in version 3.4.
</div>
</dd></dl>

<dl class="data">
<dt id="doctest.REPORTING_FLAGS">
<code class="descclassname">doctest.</code><code class="descname">REPORTING_FLAGS</code><a class="headerlink" href="#doctest.REPORTING_FLAGS" title="Permalink to this definition">¶</a></dt>
<dd>A bitmask or’ing together all the reporting flags above.
</dd></dl>

There is also a way to register new option flag names, though this isn’t
useful unless you intend to extend <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> internals via subclassing:
<dl class="function">
<dt id="doctest.register_optionflag">
<code class="descclassname">doctest.</code><code class="descname">register_optionflag</code>(name)<a class="headerlink" href="#doctest.register_optionflag" title="Permalink to this definition">¶</a></dt>
<dd>Create a new option flag with a given name, and return the new flag’s integer
value. <a class="reference internal" href="#doctest.register_optionflag" title="doctest.register_optionflag"><code class="xref py py-func docutils literal notranslate">register_optionflag()</code></a> can be used when subclassing
<a class="reference internal" href="#doctest.OutputChecker" title="doctest.OutputChecker"><code class="xref py py-class docutils literal notranslate">OutputChecker</code></a> or <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a> to create new options that are
supported by your subclasses. <a class="reference internal" href="#doctest.register_optionflag" title="doctest.register_optionflag"><code class="xref py py-func docutils literal notranslate">register_optionflag()</code></a> should always be
called using the following idiom:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>MY_FLAG = register_optionflag(&#39;MY_FLAG&#39;)
</pre></div>
</div>
</dd></dl>

</div>
<div class="section" id="directives">
<h3>26.3.3.6. Directives<a class="headerlink" href="#directives" title="Permalink to this headline">¶</a></h3>
Doctest directives may be used to modify the <a class="reference internal" href="#doctest-options">option flags</a> for an individual example. Doctest directives are
special Python comments following an example’s source code:
<pre>
directive ::= &quot;#&quot; &quot;doctest:&quot; <a class="reference internal" href="#grammar-token-directive_options"><code class="xref docutils literal notranslate">directive_options</code></a>
directive_options ::= <a class="reference internal" href="#grammar-token-directive_option"><code class="xref docutils literal notranslate">directive_option</code></a> (&quot;,&quot; <a class="reference internal" href="#grammar-token-directive_option"><code class="xref docutils literal notranslate">directive_option</code></a>)\*
directive_option ::= <a class="reference internal" href="#grammar-token-on_or_off"><code class="xref docutils literal notranslate">on_or_off</code></a> <a class="reference internal" href="#grammar-token-directive_option_name"><code class="xref docutils literal notranslate">directive_option_name</code></a>
on_or_off ::= &quot;+&quot; \| &quot;-&quot;
directive_option_name ::= &quot;DONT_ACCEPT_BLANKLINE&quot; \| &quot;NORMALIZE_WHITESPACE&quot; \| ...
</pre>
Whitespace is not allowed between the <code class="docutils literal notranslate">+</code> or <code class="docutils literal notranslate">-</code> and the directive option
name. The directive option name can be any of the option flag names explained
above.
An example’s doctest directives modify doctest’s behavior for that single
example. Use <code class="docutils literal notranslate">+</code> to enable the named behavior, or <code class="docutils literal notranslate">-</code> to disable it.
For example, this test passes:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; print(list(range(20))) # doctest: +NORMALIZE_WHITESPACE
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
</pre></div>
</div>
Without the directive it would fail, both because the actual output doesn’t have
two blanks before the single-digit list elements, and because the actual output
is on a single line. This test also passes, and also requires a directive to do
so:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; print(list(range(20))) # doctest: +ELLIPSIS
[0, 1, ..., 18, 19]
</pre></div>
</div>
Multiple directives can be used on a single physical line, separated by
commas:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; print(list(range(20))) # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
[0, 1, ..., 18, 19]
</pre></div>
</div>
If multiple directive comments are used for a single example, then they are
combined:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; print(list(range(20))) # doctest: +ELLIPSIS
... # doctest: +NORMALIZE_WHITESPACE
[0, 1, ..., 18, 19]
</pre></div>
</div>
As the previous example shows, you can add <code class="docutils literal notranslate">...</code> lines to your example
containing only directives. This can be useful when an example is too long for
a directive to comfortably fit on the same line:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; print(list(range(5)) + list(range(10, 20)) + list(range(30, 40)))
... # doctest: +ELLIPSIS
[0, ..., 4, 10, ..., 19, 30, ..., 39]
</pre></div>
</div>
Note that since all options are disabled by default, and directives apply only
to the example they appear in, enabling options (via <code class="docutils literal notranslate">+</code> in a directive) is
usually the only meaningful choice. However, option flags can also be passed to
functions that run doctests, establishing different defaults. In such cases,
disabling an option via <code class="docutils literal notranslate">-</code> in a directive can be useful.
</div>
<div class="section" id="warnings">
<h3>26.3.3.7. Warnings<a class="headerlink" href="#warnings" title="Permalink to this headline">¶</a></h3>
<a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> is serious about requiring exact matches in expected output. If
even a single character doesn’t match, the test fails. This will probably
surprise you a few times, as you learn exactly what Python does and doesn’t
guarantee about output. For example, when printing a dict, Python doesn’t
guarantee that the key-value pairs will be printed in any particular order, so a
test like
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; foo()
{&quot;Hermione&quot;: &quot;hippogryph&quot;, &quot;Harry&quot;: &quot;broomstick&quot;}
</pre></div>
</div>
is vulnerable! One workaround is to do
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; foo() == {&quot;Hermione&quot;: &quot;hippogryph&quot;, &quot;Harry&quot;: &quot;broomstick&quot;}
True
</pre></div>
</div>
instead. Another is to do
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; d = sorted(foo().items())
&gt;&gt;&gt; d
[(&#39;Harry&#39;, &#39;broomstick&#39;), (&#39;Hermione&#39;, &#39;hippogryph&#39;)]
</pre></div>
</div>
There are others, but you get the idea.
Another bad idea is to print things that embed an object address, like
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; id(1.0) # certain to fail some of the time
7948648
&gt;&gt;&gt; class C: pass
&gt;&gt;&gt; C() # the default repr() for instances embeds an address
&lt;__main__.C instance at 0x00AC18F0&gt;
</pre></div>
</div>
The <a class="reference internal" href="#doctest.ELLIPSIS" title="doctest.ELLIPSIS"><code class="xref py py-const docutils literal notranslate">ELLIPSIS</code></a> directive gives a nice approach for the last example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; C() #doctest: +ELLIPSIS
&lt;__main__.C instance at 0x...&gt;
</pre></div>
</div>
Floating-point numbers are also subject to small output variations across
platforms, because Python defers to the platform C library for float formatting,
and C libraries vary widely in quality here.
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; 1./7 # risky
0.14285714285714285
&gt;&gt;&gt; print(1./7) # safer
0.142857142857
&gt;&gt;&gt; print(round(1./7, 6)) # much safer
0.142857
</pre></div>
</div>
Numbers of the form <code class="docutils literal notranslate">I/2.**J</code> are safe across all platforms, and I often
contrive doctest examples to produce numbers of that form:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; 3./4 # utterly safe
0.75
</pre></div>
</div>
Simple fractions are also easier for people to understand, and that makes for
better documentation.
</div>
</div>
<div class="section" id="basic-api">
<h2>26.3.4. Basic API<a class="headerlink" href="#basic-api" title="Permalink to this headline">¶</a></h2>
The functions <a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a> and <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a> provide a simple interface to
doctest that should be sufficient for most basic uses. For a less formal
introduction to these two functions, see sections <a class="reference internal" href="#doctest-simple-testmod">Simple Usage: Checking Examples in Docstrings</a>
and <a class="reference internal" href="#doctest-simple-testfile">Simple Usage: Checking Examples in a Text File</a>.
<dl class="function">
<dt id="doctest.testfile">
<code class="descclassname">doctest.</code><code class="descname">testfile</code>(filename, module_relative=True, name=None, package=None, globs=None, verbose=None, report=True, optionflags=0, extraglobs=None, raise_on_error=False, parser=DocTestParser(), encoding=None)<a class="headerlink" href="#doctest.testfile" title="Permalink to this definition">¶</a></dt>
<dd>All arguments except filename are optional, and should be specified in keyword
form.
Test examples in the file named filename. Return <code class="docutils literal notranslate">(failure_count,
test_count)</code>.
Optional argument module_relative specifies how the filename should be
interpreted:
<ul class="simple">
<li>If module_relative is <code class="docutils literal notranslate">True</code> (the default), then filename specifies an
OS-independent module-relative path. By default, this path is relative to the
calling module’s directory; but if the package argument is specified, then it
is relative to that package. To ensure OS-independence, filename should use
<code class="docutils literal notranslate">/</code> characters to separate path segments, and may not be an absolute path
(i.e., it may not begin with <code class="docutils literal notranslate">/</code>).</li>
<li>If module_relative is <code class="docutils literal notranslate">False</code>, then filename specifies an OS-specific
path. The path may be absolute or relative; relative paths are resolved with
respect to the current working directory.</li>
</ul>
Optional argument name gives the name of the test; by default, or if <code class="docutils literal notranslate">None</code>,
<code class="docutils literal notranslate">os.path.basename(filename)</code> is used.
Optional argument package is a Python package or the name of a Python package
whose directory should be used as the base directory for a module-relative
filename. If no package is specified, then the calling module’s directory is
used as the base directory for module-relative filenames. It is an error to
specify package if module_relative is <code class="docutils literal notranslate">False</code>.
Optional argument globs gives a dict to be used as the globals when executing
examples. A new shallow copy of this dict is created for the doctest, so its
examples start with a clean slate. By default, or if <code class="docutils literal notranslate">None</code>, a new empty dict
is used.
Optional argument extraglobs gives a dict merged into the globals used to
execute examples. This works like <a class="reference internal" href="stdtypes.html#dict.update" title="dict.update"><code class="xref py py-meth docutils literal notranslate">dict.update()</code></a>: if globs and
extraglobs have a common key, the associated value in extraglobs appears in
the combined dict. By default, or if <code class="docutils literal notranslate">None</code>, no extra globals are used. This
is an advanced feature that allows parameterization of doctests. For example, a
doctest can be written for a base class, using a generic name for the class,
then reused to test any number of subclasses by passing an extraglobs dict
mapping the generic name to the subclass to be tested.
Optional argument verbose prints lots of stuff if true, and prints only
failures if false; by default, or if <code class="docutils literal notranslate">None</code>, it’s true if and only if <code class="docutils literal notranslate">'-v'</code>
is in <code class="docutils literal notranslate">sys.argv</code>.
Optional argument report prints a summary at the end when true, else prints
nothing at the end. In verbose mode, the summary is detailed, else the summary
is very brief (in fact, empty if all tests passed).
Optional argument optionflags (default value 0) takes the
<a class="reference internal" href="../reference/expressions.html#bitwise">bitwise OR</a> of option flags.
See section <a class="reference internal" href="#doctest-options">Option Flags</a>.
Optional argument raise_on_error defaults to false. If true, an exception is
raised upon the first failure or unexpected exception in an example. This
allows failures to be post-mortem debugged. Default behavior is to continue
running examples.
Optional argument parser specifies a <a class="reference internal" href="#doctest.DocTestParser" title="doctest.DocTestParser"><code class="xref py py-class docutils literal notranslate">DocTestParser</code></a> (or subclass) that
should be used to extract tests from the files. It defaults to a normal parser
(i.e., <code class="docutils literal notranslate">DocTestParser()</code>).
Optional argument encoding specifies an encoding that should be used to
convert the file to unicode.
</dd></dl>

<dl class="function">
<dt id="doctest.testmod">
<code class="descclassname">doctest.</code><code class="descname">testmod</code>(m=None, name=None, globs=None, verbose=None, report=True, optionflags=0, extraglobs=None, raise_on_error=False, exclude_empty=False)<a class="headerlink" href="#doctest.testmod" title="Permalink to this definition">¶</a></dt>
<dd>All arguments are optional, and all except for m should be specified in
keyword form.
Test examples in docstrings in functions and classes reachable from module m
(or module <a class="reference internal" href="__main__.html#module-__main__" title="__main__: The environment where the top-level script is run."><code class="xref py py-mod docutils literal notranslate">__main__</code></a> if m is not supplied or is <code class="docutils literal notranslate">None</code>), starting with
<code class="docutils literal notranslate">m.__doc__</code>.
Also test examples reachable from dict <code class="docutils literal notranslate">m.__test__</code>, if it exists and is not
<code class="docutils literal notranslate">None</code>. <code class="docutils literal notranslate">m.__test__</code> maps names (strings) to functions, classes and
strings; function and class docstrings are searched for examples; strings are
searched directly, as if they were docstrings.
Only docstrings attached to objects belonging to module m are searched.
Return <code class="docutils literal notranslate">(failure_count, test_count)</code>.
Optional argument name gives the name of the module; by default, or if
<code class="docutils literal notranslate">None</code>, <code class="docutils literal notranslate">m.__name__</code> is used.
Optional argument exclude_empty defaults to false. If true, objects for which
no doctests are found are excluded from consideration. The default is a backward
compatibility hack, so that code still using <code class="xref py py-meth docutils literal notranslate">doctest.master.summarize()</code> in
conjunction with <a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a> continues to get output for objects with no
tests. The exclude_empty argument to the newer <a class="reference internal" href="#doctest.DocTestFinder" title="doctest.DocTestFinder"><code class="xref py py-class docutils literal notranslate">DocTestFinder</code></a>
constructor defaults to true.
Optional arguments extraglobs, verbose, report, optionflags,
raise_on_error, and globs are the same as for function <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a>
above, except that globs defaults to <code class="docutils literal notranslate">m.__dict__</code>.
</dd></dl>

<dl class="function">
<dt id="doctest.run_docstring_examples">
<code class="descclassname">doctest.</code><code class="descname">run_docstring_examples</code>(f, globs, verbose=False, name=&quot;NoName&quot;, compileflags=None, optionflags=0)<a class="headerlink" href="#doctest.run_docstring_examples" title="Permalink to this definition">¶</a></dt>
<dd>Test examples associated with object f; for example, f may be a string,
a module, a function, or a class object.
A shallow copy of dictionary argument globs is used for the execution context.
Optional argument name is used in failure messages, and defaults to
<code class="docutils literal notranslate">&quot;NoName&quot;</code>.
If optional argument verbose is true, output is generated even if there are no
failures. By default, output is generated only in case of an example failure.
Optional argument compileflags gives the set of flags that should be used by
the Python compiler when running the examples. By default, or if <code class="docutils literal notranslate">None</code>,
flags are deduced corresponding to the set of future features found in globs.
Optional argument optionflags works as for function <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a> above.
</dd></dl>

</div>
<div class="section" id="unittest-api">
<h2>26.3.5. Unittest API<a class="headerlink" href="#unittest-api" title="Permalink to this headline">¶</a></h2>
As your collection of doctest’ed modules grows, you’ll want a way to run all
their doctests systematically. <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> provides two functions that can
be used to create <a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> test suites from modules and text files
containing doctests. To integrate with <a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> test discovery, include
a <code class="xref py py-func docutils literal notranslate">load_tests()</code> function in your test module:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>import unittest
import doctest
import my_module_with_doctests

def load_tests(loader, tests, ignore):
 tests.addTests(doctest.DocTestSuite(my_module_with_doctests))
 return tests
</pre></div>
</div>
There are two main functions for creating <a class="reference internal" href="unittest.html#unittest.TestSuite" title="unittest.TestSuite"><code class="xref py py-class docutils literal notranslate">unittest.TestSuite</code></a> instances
from text files and modules with doctests:
<dl class="function">
<dt id="doctest.DocFileSuite">
<code class="descclassname">doctest.</code><code class="descname">DocFileSuite</code>(*paths, module_relative=True, package=None, setUp=None, tearDown=None, globs=None, optionflags=0, parser=DocTestParser(), encoding=None)<a class="headerlink" href="#doctest.DocFileSuite" title="Permalink to this definition">¶</a></dt>
<dd>Convert doctest tests from one or more text files to a
<a class="reference internal" href="unittest.html#unittest.TestSuite" title="unittest.TestSuite"><code class="xref py py-class docutils literal notranslate">unittest.TestSuite</code></a>.
The returned <a class="reference internal" href="unittest.html#unittest.TestSuite" title="unittest.TestSuite"><code class="xref py py-class docutils literal notranslate">unittest.TestSuite</code></a> is to be run by the unittest framework
and runs the interactive examples in each file. If an example in any file
fails, then the synthesized unit test fails, and a <code class="xref py py-exc docutils literal notranslate">failureException</code>
exception is raised showing the name of the file containing the test and a
(sometimes approximate) line number.
Pass one or more paths (as strings) to text files to be examined.
Options may be provided as keyword arguments:
Optional argument module_relative specifies how the filenames in paths
should be interpreted:
<ul class="simple">
<li>If module_relative is <code class="docutils literal notranslate">True</code> (the default), then each filename in
paths specifies an OS-independent module-relative path. By default, this
path is relative to the calling module’s directory; but if the package
argument is specified, then it is relative to that package. To ensure
OS-independence, each filename should use <code class="docutils literal notranslate">/</code> characters to separate path
segments, and may not be an absolute path (i.e., it may not begin with
<code class="docutils literal notranslate">/</code>).</li>
<li>If module_relative is <code class="docutils literal notranslate">False</code>, then each filename in paths specifies
an OS-specific path. The path may be absolute or relative; relative paths
are resolved with respect to the current working directory.</li>
</ul>
Optional argument package is a Python package or the name of a Python
package whose directory should be used as the base directory for
module-relative filenames in paths. If no package is specified, then the
calling module’s directory is used as the base directory for module-relative
filenames. It is an error to specify package if module_relative is
<code class="docutils literal notranslate">False</code>.
Optional argument setUp specifies a set-up function for the test suite.
This is called before running the tests in each file. The setUp function
will be passed a <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> object. The setUp function can access the
test globals as the globs attribute of the test passed.
Optional argument tearDown specifies a tear-down function for the test
suite. This is called after running the tests in each file. The tearDown
function will be passed a <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> object. The setUp function can
access the test globals as the globs attribute of the test passed.
Optional argument globs is a dictionary containing the initial global
variables for the tests. A new copy of this dictionary is created for each
test. By default, globs is a new empty dictionary.
Optional argument optionflags specifies the default doctest options for the
tests, created by or-ing together individual option flags. See section
<a class="reference internal" href="#doctest-options">Option Flags</a>. See function <a class="reference internal" href="#doctest.set_unittest_reportflags" title="doctest.set_unittest_reportflags"><code class="xref py py-func docutils literal notranslate">set_unittest_reportflags()</code></a> below
for a better way to set reporting options.
Optional argument parser specifies a <a class="reference internal" href="#doctest.DocTestParser" title="doctest.DocTestParser"><code class="xref py py-class docutils literal notranslate">DocTestParser</code></a> (or subclass)
that should be used to extract tests from the files. It defaults to a normal
parser (i.e., <code class="docutils literal notranslate">DocTestParser()</code>).
Optional argument encoding specifies an encoding that should be used to
convert the file to unicode.
The global <code class="docutils literal notranslate">__file__</code> is added to the globals provided to doctests loaded
from a text file using <a class="reference internal" href="#doctest.DocFileSuite" title="doctest.DocFileSuite"><code class="xref py py-func docutils literal notranslate">DocFileSuite()</code></a>.
</dd></dl>

<dl class="function">
<dt id="doctest.DocTestSuite">
<code class="descclassname">doctest.</code><code class="descname">DocTestSuite</code>(module=None, globs=None, extraglobs=None, test_finder=None, setUp=None, tearDown=None, checker=None)<a class="headerlink" href="#doctest.DocTestSuite" title="Permalink to this definition">¶</a></dt>
<dd>Convert doctest tests for a module to a <a class="reference internal" href="unittest.html#unittest.TestSuite" title="unittest.TestSuite"><code class="xref py py-class docutils literal notranslate">unittest.TestSuite</code></a>.
The returned <a class="reference internal" href="unittest.html#unittest.TestSuite" title="unittest.TestSuite"><code class="xref py py-class docutils literal notranslate">unittest.TestSuite</code></a> is to be run by the unittest framework
and runs each doctest in the module. If any of the doctests fail, then the
synthesized unit test fails, and a <code class="xref py py-exc docutils literal notranslate">failureException</code> exception is raised
showing the name of the file containing the test and a (sometimes approximate)
line number.
Optional argument module provides the module to be tested. It can be a module
object or a (possibly dotted) module name. If not specified, the module calling
this function is used.
Optional argument globs is a dictionary containing the initial global
variables for the tests. A new copy of this dictionary is created for each
test. By default, globs is a new empty dictionary.
Optional argument extraglobs specifies an extra set of global variables, which
is merged into globs. By default, no extra globals are used.
Optional argument test_finder is the <a class="reference internal" href="#doctest.DocTestFinder" title="doctest.DocTestFinder"><code class="xref py py-class docutils literal notranslate">DocTestFinder</code></a> object (or a
drop-in replacement) that is used to extract doctests from the module.
Optional arguments setUp, tearDown, and optionflags are the same as for
function <a class="reference internal" href="#doctest.DocFileSuite" title="doctest.DocFileSuite"><code class="xref py py-func docutils literal notranslate">DocFileSuite()</code></a> above.
This function uses the same search technique as <a class="reference internal" href="#doctest.testmod" title="doctest.testmod"><code class="xref py py-func docutils literal notranslate">testmod()</code></a>.
<div class="versionchanged">
Changed in version 3.5: <a class="reference internal" href="#doctest.DocTestSuite" title="doctest.DocTestSuite"><code class="xref py py-func docutils literal notranslate">DocTestSuite()</code></a> returns an empty <a class="reference internal" href="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="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a>.
</div>
</dd></dl>

Under the covers, <a class="reference internal" href="#doctest.DocTestSuite" title="doctest.DocTestSuite"><code class="xref py py-func docutils literal notranslate">DocTestSuite()</code></a> creates a <a class="reference internal" href="unittest.html#unittest.TestSuite" title="unittest.TestSuite"><code class="xref py py-class docutils literal notranslate">unittest.TestSuite</code></a> out
of <code class="xref py py-class docutils literal notranslate">doctest.DocTestCase</code> instances, and <code class="xref py py-class docutils literal notranslate">DocTestCase</code> is a
subclass of <a class="reference internal" href="unittest.html#unittest.TestCase" title="unittest.TestCase"><code class="xref py py-class docutils literal notranslate">unittest.TestCase</code></a>. <code class="xref py py-class docutils literal notranslate">DocTestCase</code> isn’t documented
here (it’s an internal detail), but studying its code can answer questions about
the exact details of <a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> integration.
Similarly, <a class="reference internal" href="#doctest.DocFileSuite" title="doctest.DocFileSuite"><code class="xref py py-func docutils literal notranslate">DocFileSuite()</code></a> creates a <a class="reference internal" href="unittest.html#unittest.TestSuite" title="unittest.TestSuite"><code class="xref py py-class docutils literal notranslate">unittest.TestSuite</code></a> out of
<code class="xref py py-class docutils literal notranslate">doctest.DocFileCase</code> instances, and <code class="xref py py-class docutils literal notranslate">DocFileCase</code> is a subclass
of <code class="xref py py-class docutils literal notranslate">DocTestCase</code>.
So both ways of creating a <a class="reference internal" href="unittest.html#unittest.TestSuite" title="unittest.TestSuite"><code class="xref py py-class docutils literal notranslate">unittest.TestSuite</code></a> run instances of
<code class="xref py py-class docutils literal notranslate">DocTestCase</code>. This is important for a subtle reason: when you run
<a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> functions yourself, you can control the <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> options in
use directly, by passing option flags to <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> functions. However, if
you’re writing a <a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> framework, <a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> ultimately controls
when and how tests get run. The framework author typically wants to control
<a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> reporting options (perhaps, e.g., specified by command line
options), but there’s no way to pass options through <a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> to
<a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> test runners.
For this reason, <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> also supports a notion of <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a>
reporting flags specific to <a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> support, via this function:
<dl class="function">
<dt id="doctest.set_unittest_reportflags">
<code class="descclassname">doctest.</code><code class="descname">set_unittest_reportflags</code>(flags)<a class="headerlink" href="#doctest.set_unittest_reportflags" title="Permalink to this definition">¶</a></dt>
<dd>Set the <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> reporting flags to use.
Argument flags takes the <a class="reference internal" href="../reference/expressions.html#bitwise">bitwise OR</a> of option flags. See
section <a class="reference internal" href="#doctest-options">Option Flags</a>. Only “reporting flags” can be used.
This is a module-global setting, and affects all future doctests run by module
<a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a>: the <code class="xref py py-meth docutils literal notranslate">runTest()</code> method of <code class="xref py py-class docutils literal notranslate">DocTestCase</code> looks at
the option flags specified for the test case when the <code class="xref py py-class docutils literal notranslate">DocTestCase</code>
instance was constructed. If no reporting flags were specified (which is the
typical and expected case), <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a>’s <a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> reporting flags are
<a class="reference internal" href="../reference/expressions.html#bitwise">bitwise ORed</a> into the option flags, and the option flags
so augmented are passed to the <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a> instance created to
run the doctest. If any reporting flags were specified when the
<code class="xref py py-class docutils literal notranslate">DocTestCase</code> instance was constructed, <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a>’s
<a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> reporting flags are ignored.
The value of the <a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> reporting flags in effect before the function
was called is returned by the function.
</dd></dl>

</div>
<div class="section" id="advanced-api">
<h2>26.3.6. Advanced API<a class="headerlink" href="#advanced-api" title="Permalink to this headline">¶</a></h2>
The basic API is a simple wrapper that’s intended to make doctest easy to use.
It is fairly flexible, and should meet most users’ needs; however, if you
require more fine-grained control over testing, or wish to extend doctest’s
capabilities, then you should use the advanced API.
The advanced API revolves around two container classes, which are used to store
the interactive examples extracted from doctest cases:
<ul class="simple">
<li><a class="reference internal" href="#doctest.Example" title="doctest.Example"><code class="xref py py-class docutils literal notranslate">Example</code></a>: A single Python <a class="reference internal" href="../glossary.html#term-statement">statement</a>, paired with its expected
output.</li>
<li><a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a>: A collection of <a class="reference internal" href="#doctest.Example" title="doctest.Example"><code class="xref py py-class docutils literal notranslate">Example</code></a>s, typically extracted
from a single docstring or text file.</li>
</ul>
Additional processing classes are defined to find, parse, and run, and check
doctest examples:
<ul class="simple">
<li><a class="reference internal" href="#doctest.DocTestFinder" title="doctest.DocTestFinder"><code class="xref py py-class docutils literal notranslate">DocTestFinder</code></a>: Finds all docstrings in a given module, and uses a
<a class="reference internal" href="#doctest.DocTestParser" title="doctest.DocTestParser"><code class="xref py py-class docutils literal notranslate">DocTestParser</code></a> to create a <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> from every docstring that
contains interactive examples.</li>
<li><a class="reference internal" href="#doctest.DocTestParser" title="doctest.DocTestParser"><code class="xref py py-class docutils literal notranslate">DocTestParser</code></a>: Creates a <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> object from a string (such
as an object’s docstring).</li>
<li><a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a>: Executes the examples in a <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a>, and uses
an <a class="reference internal" href="#doctest.OutputChecker" title="doctest.OutputChecker"><code class="xref py py-class docutils literal notranslate">OutputChecker</code></a> to verify their output.</li>
<li><a class="reference internal" href="#doctest.OutputChecker" title="doctest.OutputChecker"><code class="xref py py-class docutils literal notranslate">OutputChecker</code></a>: Compares the actual output from a doctest example with
the expected output, and decides whether they match.</li>
</ul>
The relationships among these processing classes are summarized in the following
diagram:
<div class="highlight-python3 notranslate"><div class="highlight"><pre> list of:
+------+ +---------+
|module| --DocTestFinder-&gt; | DocTest | --DocTestRunner-&gt; results
+------+ | ^ +---------+ | ^ (printed)
 | | | Example | | |
 v | | ... | v |
 DocTestParser | Example | OutputChecker
 +---------+
</pre></div>
</div>
<div class="section" id="doctest-objects">
<h3>26.3.6.1. DocTest Objects<a class="headerlink" href="#doctest-objects" title="Permalink to this headline">¶</a></h3>
<dl class="class">
<dt id="doctest.DocTest">
class <code class="descclassname">doctest.</code><code class="descname">DocTest</code>(examples, globs, name, filename, lineno, docstring)<a class="headerlink" href="#doctest.DocTest" title="Permalink to this definition">¶</a></dt>
<dd>A collection of doctest examples that should be run in a single namespace. The
constructor arguments are used to initialize the attributes of the same names.
<a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> defines the following attributes. They are initialized by
the constructor, and should not be modified directly.
<dl class="attribute">
<dt id="doctest.DocTest.examples">
<code class="descname">examples</code><a class="headerlink" href="#doctest.DocTest.examples" title="Permalink to this definition">¶</a></dt>
<dd>A list of <a class="reference internal" href="#doctest.Example" title="doctest.Example"><code class="xref py py-class docutils literal notranslate">Example</code></a> objects encoding the individual interactive Python
examples that should be run by this test.
</dd></dl>

<dl class="attribute">
<dt id="doctest.DocTest.globs">
<code class="descname">globs</code><a class="headerlink" href="#doctest.DocTest.globs" title="Permalink to this definition">¶</a></dt>
<dd>The namespace (aka globals) that the examples should be run in. This is a
dictionary mapping names to values. Any changes to the namespace made by the
examples (such as binding new variables) will be reflected in <a class="reference internal" href="#doctest.DocTest.globs" title="doctest.DocTest.globs"><code class="xref py py-attr docutils literal notranslate">globs</code></a>
after the test is run.
</dd></dl>

<dl class="attribute">
<dt id="doctest.DocTest.name">
<code class="descname">name</code><a class="headerlink" href="#doctest.DocTest.name" title="Permalink to this definition">¶</a></dt>
<dd>A string name identifying the <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a>. Typically, this is the name
of the object or file that the test was extracted from.
</dd></dl>

<dl class="attribute">
<dt id="doctest.DocTest.filename">
<code class="descname">filename</code><a class="headerlink" href="#doctest.DocTest.filename" title="Permalink to this definition">¶</a></dt>
<dd>The name of the file that this <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> was extracted from; or
<code class="docutils literal notranslate">None</code> if the filename is unknown, or if the <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> was not
extracted from a file.
</dd></dl>

<dl class="attribute">
<dt id="doctest.DocTest.lineno">
<code class="descname">lineno</code><a class="headerlink" href="#doctest.DocTest.lineno" title="Permalink to this definition">¶</a></dt>
<dd>The line number within <a class="reference internal" href="#doctest.DocTest.filename" title="doctest.DocTest.filename"><code class="xref py py-attr docutils literal notranslate">filename</code></a> where this <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> begins, or
<code class="docutils literal notranslate">None</code> if the line number is unavailable. This line number is zero-based
with respect to the beginning of the file.
</dd></dl>

<dl class="attribute">
<dt id="doctest.DocTest.docstring">
<code class="descname">docstring</code><a class="headerlink" href="#doctest.DocTest.docstring" title="Permalink to this definition">¶</a></dt>
<dd>The string that the test was extracted from, or <code class="docutils literal notranslate">None</code> if the string is
unavailable, or if the test was not extracted from a string.
</dd></dl>

</dd></dl>

</div>
<div class="section" id="example-objects">
<h3>26.3.6.2. Example Objects<a class="headerlink" href="#example-objects" title="Permalink to this headline">¶</a></h3>
<dl class="class">
<dt id="doctest.Example">
class <code class="descclassname">doctest.</code><code class="descname">Example</code>(source, want, exc_msg=None, lineno=0, indent=0, options=None)<a class="headerlink" href="#doctest.Example" title="Permalink to this definition">¶</a></dt>
<dd>A single interactive example, consisting of a Python statement and its expected
output. The constructor arguments are used to initialize the attributes of
the same names.
<a class="reference internal" href="#doctest.Example" title="doctest.Example"><code class="xref py py-class docutils literal notranslate">Example</code></a> defines the following attributes. They are initialized by
the constructor, and should not be modified directly.
<dl class="attribute">
<dt id="doctest.Example.source">
<code class="descname">source</code><a class="headerlink" href="#doctest.Example.source" title="Permalink to this definition">¶</a></dt>
<dd>A string containing the example’s source code. This source code consists of a
single Python statement, and always ends with a newline; the constructor adds
a newline when necessary.
</dd></dl>

<dl class="attribute">
<dt id="doctest.Example.want">
<code class="descname">want</code><a class="headerlink" href="#doctest.Example.want" title="Permalink to this definition">¶</a></dt>
<dd>The expected output from running the example’s source code (either from
stdout, or a traceback in case of exception). <a class="reference internal" href="#doctest.Example.want" title="doctest.Example.want"><code class="xref py py-attr docutils literal notranslate">want</code></a> ends with a
newline unless no output is expected, in which case it’s an empty string. The
constructor adds a newline when necessary.
</dd></dl>

<dl class="attribute">
<dt id="doctest.Example.exc_msg">
<code class="descname">exc_msg</code><a class="headerlink" href="#doctest.Example.exc_msg" title="Permalink to this definition">¶</a></dt>
<dd>The exception message generated by the example, if the example is expected to
generate an exception; or <code class="docutils literal notranslate">None</code> if it is not expected to generate an
exception. This exception message is compared against the return value of
<a class="reference internal" href="traceback.html#traceback.format_exception_only" title="traceback.format_exception_only"><code class="xref py py-func docutils literal notranslate">traceback.format_exception_only()</code></a>. <a class="reference internal" href="#doctest.Example.exc_msg" title="doctest.Example.exc_msg"><code class="xref py py-attr docutils literal notranslate">exc_msg</code></a> ends with a newline
unless it’s <code class="docutils literal notranslate">None</code>. The constructor adds a newline if needed.
</dd></dl>

<dl class="attribute">
<dt id="doctest.Example.lineno">
<code class="descname">lineno</code><a class="headerlink" href="#doctest.Example.lineno" title="Permalink to this definition">¶</a></dt>
<dd>The line number within the string containing this example where the example
begins. This line number is zero-based with respect to the beginning of the
containing string.
</dd></dl>

<dl class="attribute">
<dt id="doctest.Example.indent">
<code class="descname">indent</code><a class="headerlink" href="#doctest.Example.indent" title="Permalink to this definition">¶</a></dt>
<dd>The example’s indentation in the containing string, i.e., the number of space
characters that precede the example’s first prompt.
</dd></dl>

<dl class="attribute">
<dt id="doctest.Example.options">
<code class="descname">options</code><a class="headerlink" href="#doctest.Example.options" title="Permalink to this definition">¶</a></dt>
<dd>A dictionary mapping from option flags to <code class="docutils literal notranslate">True</code> or <code class="docutils literal notranslate">False</code>, which is used
to override default options for this example. Any option flags not contained
in this dictionary are left at their default value (as specified by the
<a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a>’s <code class="xref py py-attr docutils literal notranslate">optionflags</code>). By default, no options are set.
</dd></dl>

</dd></dl>

</div>
<div class="section" id="doctestfinder-objects">
<h3>26.3.6.3. DocTestFinder objects<a class="headerlink" href="#doctestfinder-objects" title="Permalink to this headline">¶</a></h3>
<dl class="class">
<dt id="doctest.DocTestFinder">
class <code class="descclassname">doctest.</code><code class="descname">DocTestFinder</code>(verbose=False, parser=DocTestParser(), recurse=True, exclude_empty=True)<a class="headerlink" href="#doctest.DocTestFinder" title="Permalink to this definition">¶</a></dt>
<dd>A processing class used to extract the <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a>s that are relevant to
a given object, from its docstring and the docstrings of its contained objects.
<a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a>s can be extracted from modules, classes, functions,
methods, staticmethods, classmethods, and properties.
The optional argument verbose can be used to display the objects searched by
the finder. It defaults to <code class="docutils literal notranslate">False</code> (no output).
The optional argument parser specifies the <a class="reference internal" href="#doctest.DocTestParser" title="doctest.DocTestParser"><code class="xref py py-class docutils literal notranslate">DocTestParser</code></a> object (or a
drop-in replacement) that is used to extract doctests from docstrings.
If the optional argument recurse is false, then <a class="reference internal" href="#doctest.DocTestFinder.find" title="doctest.DocTestFinder.find"><code class="xref py py-meth docutils literal notranslate">DocTestFinder.find()</code></a>
will only examine the given object, and not any contained objects.
If the optional argument exclude_empty is false, then
<a class="reference internal" href="#doctest.DocTestFinder.find" title="doctest.DocTestFinder.find"><code class="xref py py-meth docutils literal notranslate">DocTestFinder.find()</code></a> will include tests for objects with empty docstrings.
<a class="reference internal" href="#doctest.DocTestFinder" title="doctest.DocTestFinder"><code class="xref py py-class docutils literal notranslate">DocTestFinder</code></a> defines the following method:
<dl class="method">
<dt id="doctest.DocTestFinder.find">
<code class="descname">find</code>(obj[, name][, module][, globs][, extraglobs])<a class="headerlink" href="#doctest.DocTestFinder.find" title="Permalink to this definition">¶</a></dt>
<dd>Return a list of the <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a>s that are defined by obj’s
docstring, or by any of its contained objects’ docstrings.
The optional argument name specifies the object’s name; this name will be
used to construct names for the returned <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a>s. If name is
not specified, then <code class="docutils literal notranslate">obj.__name__</code> is used.
The optional parameter module is the module that contains the given object.
If the module is not specified or is <code class="docutils literal notranslate">None</code>, then the test finder will attempt
to automatically determine the correct module. The object’s module is used:
<ul class="simple">
<li>As a default namespace, if globs is not specified.</li>
<li>To prevent the DocTestFinder from extracting DocTests from objects that are
imported from other modules. (Contained objects with modules other than
module are ignored.)</li>
<li>To find the name of the file containing the object.</li>
<li>To help find the line number of the object within its file.</li>
</ul>
If module is <code class="docutils literal notranslate">False</code>, no attempt to find the module will be made. This is
obscure, of use mostly in testing doctest itself: if module is <code class="docutils literal notranslate">False</code>, or
is <code class="docutils literal notranslate">None</code> but cannot be found automatically, then all objects are considered
to belong to the (non-existent) module, so all contained objects will
(recursively) be searched for doctests.
The globals for each <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> is formed by combining globs and
extraglobs (bindings in extraglobs override bindings in globs). A new
shallow copy of the globals dictionary is created for each <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a>.
If globs is not specified, then it defaults to the module’s __dict__, if
specified, or <code class="docutils literal notranslate">{}</code> otherwise. If extraglobs is not specified, then it
defaults to <code class="docutils literal notranslate">{}</code>.
</dd></dl>

</dd></dl>

</div>
<div class="section" id="doctestparser-objects">
<h3>26.3.6.4. DocTestParser objects<a class="headerlink" href="#doctestparser-objects" title="Permalink to this headline">¶</a></h3>
<dl class="class">
<dt id="doctest.DocTestParser">
class <code class="descclassname">doctest.</code><code class="descname">DocTestParser</code><a class="headerlink" href="#doctest.DocTestParser" title="Permalink to this definition">¶</a></dt>
<dd>A processing class used to extract interactive examples from a string, and use
them to create a <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> object.
<a class="reference internal" href="#doctest.DocTestParser" title="doctest.DocTestParser"><code class="xref py py-class docutils literal notranslate">DocTestParser</code></a> defines the following methods:
<dl class="method">
<dt id="doctest.DocTestParser.get_doctest">
<code class="descname">get_doctest</code>(string, globs, name, filename, lineno)<a class="headerlink" href="#doctest.DocTestParser.get_doctest" title="Permalink to this definition">¶</a></dt>
<dd>Extract all doctest examples from the given string, and collect them into a
<a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> object.
globs, name, filename, and lineno are attributes for the new
<a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> object. See the documentation for <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> for more
information.
</dd></dl>

<dl class="method">
<dt id="doctest.DocTestParser.get_examples">
<code class="descname">get_examples</code>(string, name='&lt;string&gt;')<a class="headerlink" href="#doctest.DocTestParser.get_examples" title="Permalink to this definition">¶</a></dt>
<dd>Extract all doctest examples from the given string, and return them as a list
of <a class="reference internal" href="#doctest.Example" title="doctest.Example"><code class="xref py py-class docutils literal notranslate">Example</code></a> objects. Line numbers are 0-based. The optional argument
name is a name identifying this string, and is only used for error messages.
</dd></dl>

<dl class="method">
<dt id="doctest.DocTestParser.parse">
<code class="descname">parse</code>(string, name='&lt;string&gt;')<a class="headerlink" href="#doctest.DocTestParser.parse" title="Permalink to this definition">¶</a></dt>
<dd>Divide the given string into examples and intervening text, and return them as
a list of alternating <a class="reference internal" href="#doctest.Example" title="doctest.Example"><code class="xref py py-class docutils literal notranslate">Example</code></a>s and strings. Line numbers for the
<a class="reference internal" href="#doctest.Example" title="doctest.Example"><code class="xref py py-class docutils literal notranslate">Example</code></a>s are 0-based. The optional argument name is a name
identifying this string, and is only used for error messages.
</dd></dl>

</dd></dl>

</div>
<div class="section" id="doctestrunner-objects">
<h3>26.3.6.5. DocTestRunner objects<a class="headerlink" href="#doctestrunner-objects" title="Permalink to this headline">¶</a></h3>
<dl class="class">
<dt id="doctest.DocTestRunner">
class <code class="descclassname">doctest.</code><code class="descname">DocTestRunner</code>(checker=None, verbose=None, optionflags=0)<a class="headerlink" href="#doctest.DocTestRunner" title="Permalink to this definition">¶</a></dt>
<dd>A processing class used to execute and verify the interactive examples in a
<a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a>.
The comparison between expected outputs and actual outputs is done by an
<a class="reference internal" href="#doctest.OutputChecker" title="doctest.OutputChecker"><code class="xref py py-class docutils literal notranslate">OutputChecker</code></a>. This comparison may be customized with a number of
option flags; see section <a class="reference internal" href="#doctest-options">Option Flags</a> for more information. If the
option flags are insufficient, then the comparison may also be customized by
passing a subclass of <a class="reference internal" href="#doctest.OutputChecker" title="doctest.OutputChecker"><code class="xref py py-class docutils literal notranslate">OutputChecker</code></a> to the constructor.
The test runner’s display output can be controlled in two ways. First, an output
function can be passed to <code class="xref py py-meth docutils literal notranslate">TestRunner.run()</code>; this function will be called
with strings that should be displayed. It defaults to <code class="docutils literal notranslate">sys.stdout.write</code>. If
capturing the output is not sufficient, then the display output can be also
customized by subclassing DocTestRunner, and overriding the methods
<a class="reference internal" href="#doctest.DocTestRunner.report_start" title="doctest.DocTestRunner.report_start"><code class="xref py py-meth docutils literal notranslate">report_start()</code></a>, <a class="reference internal" href="#doctest.DocTestRunner.report_success" title="doctest.DocTestRunner.report_success"><code class="xref py py-meth docutils literal notranslate">report_success()</code></a>,
<a class="reference internal" href="#doctest.DocTestRunner.report_unexpected_exception" title="doctest.DocTestRunner.report_unexpected_exception"><code class="xref py py-meth docutils literal notranslate">report_unexpected_exception()</code></a>, and <a class="reference internal" href="#doctest.DocTestRunner.report_failure" title="doctest.DocTestRunner.report_failure"><code class="xref py py-meth docutils literal notranslate">report_failure()</code></a>.
The optional keyword argument checker specifies the <a class="reference internal" href="#doctest.OutputChecker" title="doctest.OutputChecker"><code class="xref py py-class docutils literal notranslate">OutputChecker</code></a>
object (or drop-in replacement) that should be used to compare the expected
outputs to the actual outputs of doctest examples.
The optional keyword argument verbose controls the <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a>’s
verbosity. If verbose is <code class="docutils literal notranslate">True</code>, then information is printed about each
example, as it is run. If verbose is <code class="docutils literal notranslate">False</code>, then only failures are
printed. If verbose is unspecified, or <code class="docutils literal notranslate">None</code>, then verbose output is used
iff the command-line switch <code class="docutils literal notranslate">-v</code> is used.
The optional keyword argument optionflags can be used to control how the test
runner compares expected output to actual output, and how it displays failures.
For more information, see section <a class="reference internal" href="#doctest-options">Option Flags</a>.
<a class="reference internal" href="#doctest.DocTestParser" title="doctest.DocTestParser"><code class="xref py py-class docutils literal notranslate">DocTestParser</code></a> defines the following methods:
<dl class="method">
<dt id="doctest.DocTestRunner.report_start">
<code class="descname">report_start</code>(out, test, example)<a class="headerlink" href="#doctest.DocTestRunner.report_start" title="Permalink to this definition">¶</a></dt>
<dd>Report that the test runner is about to process the given example. This method
is provided to allow subclasses of <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a> to customize their
output; it should not be called directly.
example is the example about to be processed. test is the test
containing example. out is the output function that was passed to
<a class="reference internal" href="#doctest.DocTestRunner.run" title="doctest.DocTestRunner.run"><code class="xref py py-meth docutils literal notranslate">DocTestRunner.run()</code></a>.
</dd></dl>

<dl class="method">
<dt id="doctest.DocTestRunner.report_success">
<code class="descname">report_success</code>(out, test, example, got)<a class="headerlink" href="#doctest.DocTestRunner.report_success" title="Permalink to this definition">¶</a></dt>
<dd>Report that the given example ran successfully. This method is provided to
allow subclasses of <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a> to customize their output; it
should not be called directly.
example is the example about to be processed. got is the actual output
from the example. test is the test containing example. out is the
output function that was passed to <a class="reference internal" href="#doctest.DocTestRunner.run" title="doctest.DocTestRunner.run"><code class="xref py py-meth docutils literal notranslate">DocTestRunner.run()</code></a>.
</dd></dl>

<dl class="method">
<dt id="doctest.DocTestRunner.report_failure">
<code class="descname">report_failure</code>(out, test, example, got)<a class="headerlink" href="#doctest.DocTestRunner.report_failure" title="Permalink to this definition">¶</a></dt>
<dd>Report that the given example failed. This method is provided to allow
subclasses of <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a> to customize their output; it should not
be called directly.
example is the example about to be processed. got is the actual output
from the example. test is the test containing example. out is the
output function that was passed to <a class="reference internal" href="#doctest.DocTestRunner.run" title="doctest.DocTestRunner.run"><code class="xref py py-meth docutils literal notranslate">DocTestRunner.run()</code></a>.
</dd></dl>

<dl class="method">
<dt id="doctest.DocTestRunner.report_unexpected_exception">
<code class="descname">report_unexpected_exception</code>(out, test, example, exc_info)<a class="headerlink" href="#doctest.DocTestRunner.report_unexpected_exception" title="Permalink to this definition">¶</a></dt>
<dd>Report that the given example raised an unexpected exception. This method is
provided to allow subclasses of <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a> to customize their
output; it should not be called directly.
example is the example about to be processed. exc_info is a tuple
containing information about the unexpected exception (as returned by
<a class="reference internal" href="sys.html#sys.exc_info" title="sys.exc_info"><code class="xref py py-func docutils literal notranslate">sys.exc_info()</code></a>). test is the test containing example. out is the
output function that was passed to <a class="reference internal" href="#doctest.DocTestRunner.run" title="doctest.DocTestRunner.run"><code class="xref py py-meth docutils literal notranslate">DocTestRunner.run()</code></a>.
</dd></dl>

<dl class="method">
<dt id="doctest.DocTestRunner.run">
<code class="descname">run</code>(test, compileflags=None, out=None, clear_globs=True)<a class="headerlink" href="#doctest.DocTestRunner.run" title="Permalink to this definition">¶</a></dt>
<dd>Run the examples in test (a <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> object), and display the
results using the writer function out.
The examples are run in the namespace <code class="docutils literal notranslate">test.globs</code>. If clear_globs is
true (the default), then this namespace will be cleared after the test runs,
to help with garbage collection. If you would like to examine the namespace
after the test completes, then use clear_globs=False.
compileflags gives the set of flags that should be used by the Python
compiler when running the examples. If not specified, then it will default to
the set of future-import flags that apply to globs.
The output of each example is checked using the <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a>’s
output checker, and the results are formatted by the
<code class="xref py py-meth docutils literal notranslate">DocTestRunner.report_*()</code> methods.
</dd></dl>

<dl class="method">
<dt id="doctest.DocTestRunner.summarize">
<code class="descname">summarize</code>(verbose=None)<a class="headerlink" href="#doctest.DocTestRunner.summarize" title="Permalink to this definition">¶</a></dt>
<dd>Print a summary of all the test cases that have been run by this DocTestRunner,
and return a <a class="reference internal" href="../glossary.html#term-named-tuple">named tuple</a> <code class="docutils literal notranslate">TestResults(failed, attempted)</code>.
The optional verbose argument controls how detailed the summary is. If the
verbosity is not specified, then the <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a>’s verbosity is
used.
</dd></dl>

</dd></dl>

</div>
<div class="section" id="outputchecker-objects">
<h3>26.3.6.6. OutputChecker objects<a class="headerlink" href="#outputchecker-objects" title="Permalink to this headline">¶</a></h3>
<dl class="class">
<dt id="doctest.OutputChecker">
class <code class="descclassname">doctest.</code><code class="descname">OutputChecker</code><a class="headerlink" href="#doctest.OutputChecker" title="Permalink to this definition">¶</a></dt>
<dd>A class used to check the whether the actual output from a doctest example
matches the expected output. <a class="reference internal" href="#doctest.OutputChecker" title="doctest.OutputChecker"><code class="xref py py-class docutils literal notranslate">OutputChecker</code></a> defines two methods:
<a class="reference internal" href="#doctest.OutputChecker.check_output" title="doctest.OutputChecker.check_output"><code class="xref py py-meth docutils literal notranslate">check_output()</code></a>, which compares a given pair of outputs, and returns true
if they match; and <a class="reference internal" href="#doctest.OutputChecker.output_difference" title="doctest.OutputChecker.output_difference"><code class="xref py py-meth docutils literal notranslate">output_difference()</code></a>, which returns a string describing
the differences between two outputs.
<a class="reference internal" href="#doctest.OutputChecker" title="doctest.OutputChecker"><code class="xref py py-class docutils literal notranslate">OutputChecker</code></a> defines the following methods:
<dl class="method">
<dt id="doctest.OutputChecker.check_output">
<code class="descname">check_output</code>(want, got, optionflags)<a class="headerlink" href="#doctest.OutputChecker.check_output" title="Permalink to this definition">¶</a></dt>
<dd>Return <code class="docutils literal notranslate">True</code> iff the actual output from an example (got) matches the
expected output (want). These strings are always considered to match if
they are identical; but depending on what option flags the test runner is
using, several non-exact match types are also possible. See section
<a class="reference internal" href="#doctest-options">Option Flags</a> for more information about option flags.
</dd></dl>

<dl class="method">
<dt id="doctest.OutputChecker.output_difference">
<code class="descname">output_difference</code>(example, got, optionflags)<a class="headerlink" href="#doctest.OutputChecker.output_difference" title="Permalink to this definition">¶</a></dt>
<dd>Return a string describing the differences between the expected output for a
given example (example) and the actual output (got). optionflags is the
set of option flags used to compare want and got.
</dd></dl>

</dd></dl>

</div>
</div>
<div class="section" id="debugging">
<h2>26.3.7. Debugging<a class="headerlink" href="#debugging" title="Permalink to this headline">¶</a></h2>
Doctest provides several mechanisms for debugging doctest examples:
<ul>
<li>Several functions convert doctests to executable Python programs, which can be
run under the Python debugger, <a class="reference internal" href="pdb.html#module-pdb" title="pdb: The Python debugger for interactive interpreters."><code class="xref py py-mod docutils literal notranslate">pdb</code></a>.
</li>
<li>The <a class="reference internal" href="#doctest.DebugRunner" title="doctest.DebugRunner"><code class="xref py py-class docutils literal notranslate">DebugRunner</code></a> class is a subclass of <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a> that
raises an exception for the first failing example, containing information about
that example. This information can be used to perform post-mortem debugging on
the example.
</li>
<li>The <a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> cases generated by <a class="reference internal" href="#doctest.DocTestSuite" title="doctest.DocTestSuite"><code class="xref py py-func docutils literal notranslate">DocTestSuite()</code></a> support the
<a class="reference internal" href="#doctest.debug" title="doctest.debug"><code class="xref py py-meth docutils literal notranslate">debug()</code></a> method defined by <a class="reference internal" href="unittest.html#unittest.TestCase" title="unittest.TestCase"><code class="xref py py-class docutils literal notranslate">unittest.TestCase</code></a>.
</li>
<li>You can add a call to <a class="reference internal" href="pdb.html#pdb.set_trace" title="pdb.set_trace"><code class="xref py py-func docutils literal notranslate">pdb.set_trace()</code></a> in a doctest example, and you’ll
drop into the Python debugger when that line is executed. Then you can inspect
current values of variables, and so on. For example, suppose <code class="file docutils literal notranslate">a.py</code>
contains just this module docstring:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&quot;&quot;&quot;
&gt;&gt;&gt; def f(x):
... g(x*2)
&gt;&gt;&gt; def g(x):
... print(x+3)
... import pdb; pdb.set_trace()
&gt;&gt;&gt; f(3)
9
&quot;&quot;&quot;
</pre></div>
</div>
Then an interactive Python session may look like this:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; import a, doctest
&gt;&gt;&gt; doctest.testmod(a)
--Return--
&gt; &lt;doctest a[1]&gt;(3)g()-&gt;None
-&gt; import pdb; pdb.set_trace()
(Pdb) list
 1 def g(x):
 2 print(x+3)
 3 -&gt; import pdb; pdb.set_trace()
[EOF]
(Pdb) p x
6
(Pdb) step
--Return--
&gt; &lt;doctest a[0]&gt;(2)f()-&gt;None
-&gt; g(x*2)
(Pdb) list
 1 def f(x):
 2 -&gt; g(x*2)
[EOF]
(Pdb) p x
3
(Pdb) step
--Return--
&gt; &lt;doctest a[2]&gt;(1)?()-&gt;None
-&gt; f(3)
(Pdb) cont
(0, 3)
&gt;&gt;&gt;
</pre></div>
</div>
</li>
</ul>
Functions that convert doctests to Python code, and possibly run the synthesized
code under the debugger:
<dl class="function">
<dt id="doctest.script_from_examples">
<code class="descclassname">doctest.</code><code class="descname">script_from_examples</code>(s)<a class="headerlink" href="#doctest.script_from_examples" title="Permalink to this definition">¶</a></dt>
<dd>Convert text with examples to a script.
Argument s is a string containing doctest examples. The string is converted
to a Python script, where doctest examples in s are converted to regular code,
and everything else is converted to Python comments. The generated script is
returned as a string. For example,
<div class="highlight-python3 notranslate"><div class="highlight"><pre>import doctest
print(doctest.script_from_examples(r&quot;&quot;&quot;
 Set x and y to 1 and 2.
 &gt;&gt;&gt; x, y = 1, 2

Print their sum:
 &gt;&gt;&gt; print(x+y)
 3
&quot;&quot;&quot;))
</pre></div>
</div>
displays:
<div class="highlight-python3 notranslate"><div class="highlight"><pre># Set x and y to 1 and 2.
x, y = 1, 2
#
# Print their sum:
print(x+y)
# Expected:
## 3
</pre></div>
</div>
This function is used internally by other functions (see below), but can also be
useful when you want to transform an interactive Python session into a Python
script.
</dd></dl>

<dl class="function">
<dt id="doctest.testsource">
<code class="descclassname">doctest.</code><code class="descname">testsource</code>(module, name)<a class="headerlink" href="#doctest.testsource" title="Permalink to this definition">¶</a></dt>
<dd>Convert the doctest for an object to a script.
Argument module is a module object, or dotted name of a module, containing the
object whose doctests are of interest. Argument name is the name (within the
module) of the object with the doctests of interest. The result is a string,
containing the object’s docstring converted to a Python script, as described for
<a class="reference internal" href="#doctest.script_from_examples" title="doctest.script_from_examples"><code class="xref py py-func docutils literal notranslate">script_from_examples()</code></a> above. For example, if module <code class="file docutils literal notranslate">a.py</code>
contains a top-level function <code class="xref py py-func docutils literal notranslate">f()</code>, then
<div class="highlight-python3 notranslate"><div class="highlight"><pre>import a, doctest
print(doctest.testsource(a, &quot;a.f&quot;))
</pre></div>
</div>
prints a script version of function <code class="xref py py-func docutils literal notranslate">f()</code>’s docstring, with doctests
converted to code, and the rest placed in comments.
</dd></dl>

<dl class="function">
<dt id="doctest.debug">
<code class="descclassname">doctest.</code><code class="descname">debug</code>(module, name, pm=False)<a class="headerlink" href="#doctest.debug" title="Permalink to this definition">¶</a></dt>
<dd>Debug the doctests for an object.
The module and name arguments are the same as for function
<a class="reference internal" href="#doctest.testsource" title="doctest.testsource"><code class="xref py py-func docutils literal notranslate">testsource()</code></a> above. The synthesized Python script for the named object’s
docstring is written to a temporary file, and then that file is run under the
control of the Python debugger, <a class="reference internal" href="pdb.html#module-pdb" title="pdb: The Python debugger for interactive interpreters."><code class="xref py py-mod docutils literal notranslate">pdb</code></a>.
A shallow copy of <code class="docutils literal notranslate">module.__dict__</code> is used for both local and global
execution context.
Optional argument pm controls whether post-mortem debugging is used. If pm
has a true value, the script file is run directly, and the debugger gets
involved only if the script terminates via raising an unhandled exception. If
it does, then post-mortem debugging is invoked, via <a class="reference internal" href="pdb.html#pdb.post_mortem" title="pdb.post_mortem"><code class="xref py py-func docutils literal notranslate">pdb.post_mortem()</code></a>,
passing the traceback object from the unhandled exception. If pm is not
specified, or is false, the script is run under the debugger from the start, via
passing an appropriate <a class="reference internal" href="functions.html#exec" title="exec"><code class="xref py py-func docutils literal notranslate">exec()</code></a> call to <a class="reference internal" href="pdb.html#pdb.run" title="pdb.run"><code class="xref py py-func docutils literal notranslate">pdb.run()</code></a>.
</dd></dl>

<dl class="function">
<dt id="doctest.debug_src">
<code class="descclassname">doctest.</code><code class="descname">debug_src</code>(src, pm=False, globs=None)<a class="headerlink" href="#doctest.debug_src" title="Permalink to this definition">¶</a></dt>
<dd>Debug the doctests in a string.
This is like function <a class="reference internal" href="#doctest.debug" title="doctest.debug"><code class="xref py py-func docutils literal notranslate">debug()</code></a> above, except that a string containing
doctest examples is specified directly, via the src argument.
Optional argument pm has the same meaning as in function <a class="reference internal" href="#doctest.debug" title="doctest.debug"><code class="xref py py-func docutils literal notranslate">debug()</code></a> above.
Optional argument globs gives a dictionary to use as both local and global
execution context. If not specified, or <code class="docutils literal notranslate">None</code>, an empty dictionary is used.
If specified, a shallow copy of the dictionary is used.
</dd></dl>

The <a class="reference internal" href="#doctest.DebugRunner" title="doctest.DebugRunner"><code class="xref py py-class docutils literal notranslate">DebugRunner</code></a> class, and the special exceptions it may raise, are of
most interest to testing framework authors, and will only be sketched here. See
the source code, and especially <a class="reference internal" href="#doctest.DebugRunner" title="doctest.DebugRunner"><code class="xref py py-class docutils literal notranslate">DebugRunner</code></a>’s docstring (which is a
doctest!) for more details:
<dl class="class">
<dt id="doctest.DebugRunner">
class <code class="descclassname">doctest.</code><code class="descname">DebugRunner</code>(checker=None, verbose=None, optionflags=0)<a class="headerlink" href="#doctest.DebugRunner" title="Permalink to this definition">¶</a></dt>
<dd>A subclass of <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a> that raises an exception as soon as a
failure is encountered. If an unexpected exception occurs, an
<a class="reference internal" href="#doctest.UnexpectedException" title="doctest.UnexpectedException"><code class="xref py py-exc docutils literal notranslate">UnexpectedException</code></a> exception is raised, containing the test, the
example, and the original exception. If the output doesn’t match, then a
<a class="reference internal" href="#doctest.DocTestFailure" title="doctest.DocTestFailure"><code class="xref py py-exc docutils literal notranslate">DocTestFailure</code></a> exception is raised, containing the test, the example, and
the actual output.
For information about the constructor parameters and methods, see the
documentation for <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a> in section <a class="reference internal" href="#doctest-advanced-api">Advanced API</a>.
</dd></dl>

There are two exceptions that may be raised by <a class="reference internal" href="#doctest.DebugRunner" title="doctest.DebugRunner"><code class="xref py py-class docutils literal notranslate">DebugRunner</code></a> instances:
<dl class="exception">
<dt id="doctest.DocTestFailure">
exception <code class="descclassname">doctest.</code><code class="descname">DocTestFailure</code>(test, example, got)<a class="headerlink" href="#doctest.DocTestFailure" title="Permalink to this definition">¶</a></dt>
<dd>An exception raised by <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a> to signal that a doctest example’s
actual output did not match its expected output. The constructor arguments are
used to initialize the attributes of the same names.
</dd></dl>

<a class="reference internal" href="#doctest.DocTestFailure" title="doctest.DocTestFailure"><code class="xref py py-exc docutils literal notranslate">DocTestFailure</code></a> defines the following attributes:
<dl class="attribute">
<dt id="doctest.DocTestFailure.test">
<code class="descclassname">DocTestFailure.</code><code class="descname">test</code><a class="headerlink" href="#doctest.DocTestFailure.test" title="Permalink to this definition">¶</a></dt>
<dd>The <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> object that was being run when the example failed.
</dd></dl>

<dl class="attribute">
<dt id="doctest.DocTestFailure.example">
<code class="descclassname">DocTestFailure.</code><code class="descname">example</code><a class="headerlink" href="#doctest.DocTestFailure.example" title="Permalink to this definition">¶</a></dt>
<dd>The <a class="reference internal" href="#doctest.Example" title="doctest.Example"><code class="xref py py-class docutils literal notranslate">Example</code></a> that failed.
</dd></dl>

<dl class="attribute">
<dt id="doctest.DocTestFailure.got">
<code class="descclassname">DocTestFailure.</code><code class="descname">got</code><a class="headerlink" href="#doctest.DocTestFailure.got" title="Permalink to this definition">¶</a></dt>
<dd>The example’s actual output.
</dd></dl>

<dl class="exception">
<dt id="doctest.UnexpectedException">
exception <code class="descclassname">doctest.</code><code class="descname">UnexpectedException</code>(test, example, exc_info)<a class="headerlink" href="#doctest.UnexpectedException" title="Permalink to this definition">¶</a></dt>
<dd>An exception raised by <a class="reference internal" href="#doctest.DocTestRunner" title="doctest.DocTestRunner"><code class="xref py py-class docutils literal notranslate">DocTestRunner</code></a> to signal that a doctest
example raised an unexpected exception. The constructor arguments are used
to initialize the attributes of the same names.
</dd></dl>

<a class="reference internal" href="#doctest.UnexpectedException" title="doctest.UnexpectedException"><code class="xref py py-exc docutils literal notranslate">UnexpectedException</code></a> defines the following attributes:
<dl class="attribute">
<dt id="doctest.UnexpectedException.test">
<code class="descclassname">UnexpectedException.</code><code class="descname">test</code><a class="headerlink" href="#doctest.UnexpectedException.test" title="Permalink to this definition">¶</a></dt>
<dd>The <a class="reference internal" href="#doctest.DocTest" title="doctest.DocTest"><code class="xref py py-class docutils literal notranslate">DocTest</code></a> object that was being run when the example failed.
</dd></dl>

<dl class="attribute">
<dt id="doctest.UnexpectedException.example">
<code class="descclassname">UnexpectedException.</code><code class="descname">example</code><a class="headerlink" href="#doctest.UnexpectedException.example" title="Permalink to this definition">¶</a></dt>
<dd>The <a class="reference internal" href="#doctest.Example" title="doctest.Example"><code class="xref py py-class docutils literal notranslate">Example</code></a> that failed.
</dd></dl>

<dl class="attribute">
<dt id="doctest.UnexpectedException.exc_info">
<code class="descclassname">UnexpectedException.</code><code class="descname">exc_info</code><a class="headerlink" href="#doctest.UnexpectedException.exc_info" title="Permalink to this definition">¶</a></dt>
<dd>A tuple containing information about the unexpected exception, as returned by
<a class="reference internal" href="sys.html#sys.exc_info" title="sys.exc_info"><code class="xref py py-func docutils literal notranslate">sys.exc_info()</code></a>.
</dd></dl>

</div>
<div class="section" id="soapbox">
<h2>26.3.8. Soapbox<a class="headerlink" href="#soapbox" title="Permalink to this headline">¶</a></h2>
As mentioned in the introduction, <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a> has grown to have three primary
uses:
<ol class="arabic simple">
<li>Checking examples in docstrings.</li>
<li>Regression testing.</li>
<li>Executable documentation / literate testing.</li>
</ol>
These uses have different requirements, and it is important to distinguish them.
In particular, filling your docstrings with obscure test cases makes for bad
documentation.
When writing a docstring, choose docstring examples with care. There’s an art to
this that needs to be learned—it may not be natural at first. Examples should
add genuine value to the documentation. A good example can often be worth many
words. If done with care, the examples will be invaluable for your users, and
will pay back the time it takes to collect them many times over as the years go
by and things change. I’m still amazed at how often one of my <a class="reference internal" href="#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate">doctest</code></a>
examples stops working after a “harmless” change.
Doctest also makes an excellent tool for regression testing, especially if you
don’t skimp on explanatory text. By interleaving prose and examples, it becomes
much easier to keep track of what’s actually being tested, and why. When a test
fails, good prose can make it much easier to figure out what the problem is, and
how it should be fixed. It’s true that you could write extensive comments in
code-based testing, but few programmers do. Many have found that using doctest
approaches instead leads to much clearer tests. Perhaps this is simply because
doctest makes writing prose a little easier than writing code, while writing
comments in code is a little harder. I think it goes deeper than just that:
the natural attitude when writing a doctest-based test is that you want to
explain the fine points of your software, and illustrate them with examples.
This in turn naturally leads to test files that start with the simplest
features, and logically progress to complications and edge cases. A coherent
narrative is the result, instead of a collection of isolated functions that test
isolated bits of functionality seemingly at random. It’s a different attitude,
and produces different results, blurring the distinction between testing and
explaining.
Regression testing is best confined to dedicated objects or files. There are
several options for organizing tests:
<ul class="simple">
<li>Write text files containing test cases as interactive examples, and test the
files using <a class="reference internal" href="#doctest.testfile" title="doctest.testfile"><code class="xref py py-func docutils literal notranslate">testfile()</code></a> or <a class="reference internal" href="#doctest.DocFileSuite" title="doctest.DocFileSuite"><code class="xref py py-func docutils literal notranslate">DocFileSuite()</code></a>. This is recommended,
although is easiest to do for new projects, designed from the start to use
doctest.</li>
<li>Define functions named <code class="docutils literal notranslate">_regrtest_topic</code> that consist of single docstrings,
containing test cases for the named topics. These functions can be included in
the same file as the module, or separated out into a separate test file.</li>
<li>Define a <code class="docutils literal notranslate">__test__</code> dictionary mapping from regression test topics to
docstrings containing test cases.</li>
</ul>
When you have placed your tests in a module, the module can itself be the test
runner. When a test fails, you can arrange for your test runner to re-run only
the failing doctest while you debug the problem. Here is a minimal example of
such a test runner:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>if __name__ == &#39;__main__&#39;:
 import doctest
 flags = doctest.REPORT_NDIFF|doctest.FAIL_FAST
 if len(sys.argv) &gt; 1:
 name = sys.argv[1]
 if name in globals():
 obj = globals()[name]
 else:
 obj = __test__[name]
 doctest.run_docstring_examples(obj, globals(), name=name,
 optionflags=flags)
 else:
 fail, total = doctest.testmod(optionflags=flags)
 print(&quot;{} failures out of {} tests&quot;.format(fail, total))
</pre></div>
</div>
Footnotes
<table class="docutils footnote" frame="void" id="id2" rules="none">
<colgroup><col class="label" /><col /></colgroup>
<tbody valign="top">
<tr><td class="label"><a class="fn-backref" href="#id1">[1]</a></td><td>Examples containing both expected output and an exception are not supported.
Trying to guess where one ends and the other begins is too error-prone, and that
also makes for a confusing test.</td></tr>
</tbody>
</table>
</div>
</div>

</div>
 </div>
 </div>
 <div class="sphinxsidebar" role="navigation" aria-label="main navigation">
 <div class="sphinxsidebarwrapper">
 <h3><a href="../contents.html">Table Of Contents</a></h3>
 <ul>
<li><a class="reference internal" href="#">26.3. <code class="docutils literal notranslate">doctest</code> — Test interactive Python examples</a><ul>
<li><a class="reference internal" href="#simple-usage-checking-examples-in-docstrings">26.3.1. Simple Usage: Checking Examples in Docstrings</a></li>
<li><a class="reference internal" href="#simple-usage-checking-examples-in-a-text-file">26.3.2. Simple Usage: Checking Examples in a Text File</a></li>
<li><a class="reference internal" href="#how-it-works">26.3.3. How It Works</a><ul>
<li><a class="reference internal" href="#which-docstrings-are-examined">26.3.3.1. Which Docstrings Are Examined?</a></li>
<li><a class="reference internal" href="#how-are-docstring-examples-recognized">26.3.3.2. How are Docstring Examples Recognized?</a></li>
<li><a class="reference internal" href="#what-s-the-execution-context">26.3.3.3. What’s the Execution Context?</a></li>
<li><a class="reference internal" href="#what-about-exceptions">26.3.3.4. What About Exceptions?</a></li>
<li><a class="reference internal" href="#option-flags">26.3.3.5. Option Flags</a></li>
<li><a class="reference internal" href="#directives">26.3.3.6. Directives</a></li>
<li><a class="reference internal" href="#warnings">26.3.3.7. Warnings</a></li>
</ul>
</li>
<li><a class="reference internal" href="#basic-api">26.3.4. Basic API</a></li>
<li><a class="reference internal" href="#unittest-api">26.3.5. Unittest API</a></li>
<li><a class="reference internal" href="#advanced-api">26.3.6. Advanced API</a><ul>
<li><a class="reference internal" href="#doctest-objects">26.3.6.1. DocTest Objects</a></li>
<li><a class="reference internal" href="#example-objects">26.3.6.2. Example Objects</a></li>
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<li><a class="reference internal" href="#doctestrunner-objects">26.3.6.5. DocTestRunner objects</a></li>
<li><a class="reference internal" href="#outputchecker-objects">26.3.6.6. OutputChecker objects</a></li>
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<li><a class="reference internal" href="#debugging">26.3.7. Debugging</a></li>
<li><a class="reference internal" href="#soapbox">26.3.8. Soapbox</a></li>
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