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<li><a class="reference internal" href="#">Contributing</a><ul>
<li><a class="reference internal" href="#contributor-incubator">Contributor Incubator</a><ul>
<li><a class="reference internal" href="#issues-for-new-contributors">Issues for New Contributors</a></li>
</ul>
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<li><a class="reference internal" href="#submitting-a-bug-report">Submitting a bug report</a></li>
<li><a class="reference internal" href="#requesting-a-new-feature">Requesting a new feature</a></li>
<li><a class="reference internal" href="#contributing-code">Contributing code</a><ul>
<li><a class="reference internal" href="#how-to-contribute">How to contribute</a></li>
<li><a class="reference internal" href="#contributing-pull-requests">Contributing pull requests</a></li>
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<li><a class="reference internal" href="#other-ways-to-contribute">Other ways to contribute</a></li>
<li><a class="reference internal" href="#coding-guidelines">Coding guidelines</a><ul>
<li><a class="reference internal" href="#api-changes">API changes</a></li>
<li><a class="reference internal" href="#adding-new-api">Adding new API</a></li>
<li><a class="reference internal" href="#new-modules-and-files-installation">New modules and files: installation</a></li>
<li><a class="reference internal" href="#c-c-extensions">C/C++ extensions</a></li>
<li><a class="reference internal" href="#keyword-argument-processing">Keyword argument processing</a></li>
<li><a class="reference internal" href="#using-logging-for-debug-messages">Using logging for debug messages</a><ul>
<li><a class="reference internal" href="#which-logging-level-to-use">Which logging level to use?</a></li>
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<div class="section" id="contributing">
<span id="id1"></span><h1>Contributing<a class="headerlink" href="#contributing" title="Permalink to this headline">¶</a></h1>
<p>This project is a community effort, and everyone is welcome to
contribute. Everyone within the community
is expected to abide by our
<a class="reference external" href="https://github.com/matplotlib/matplotlib/blob/master/CODE_OF_CONDUCT.md">code of conduct</a>.</p>
<p>The project is hosted on
<a class="reference external" href="https://github.com/matplotlib/matplotlib">https://github.com/matplotlib/matplotlib</a></p>
<div class="section" id="contributor-incubator">
<h2>Contributor Incubator<a class="headerlink" href="#contributor-incubator" title="Permalink to this headline">¶</a></h2>
<p>If you are interested in becoming a regular contributor to Matplotlib, but
don't know where to start or feel insecure about it, you can join our non-public
communication channel for new contributors. To do so, please go to <a class="reference external" href="https://gitter.im/matplotlib/matplotlib">gitter</a> and ask to be added to '#incubator'.
This is a private gitter room moderated by core Matplotlib developers where you can
get guidance and support for your first few PRs. This is a place you can ask questions
about anything: how to use git, github, how our PR review process works, technical questions
about the code, what makes for good documentation or a blog post, how to get involved involved
in community work, or get "pre-review" on your PR.</p>
<div class="section" id="issues-for-new-contributors">
<span id="new-contributors"></span><h3>Issues for New Contributors<a class="headerlink" href="#issues-for-new-contributors" title="Permalink to this headline">¶</a></h3>
<p>While any contributions are welcome, we have marked some issues as
particularly suited for new contributors by the label
<a class="reference external" href="https://github.com/matplotlib/matplotlib/labels/good%20first%20issue">good first issue</a>
These are well documented issues, that do not require a deep understanding of
the internals of Matplotlib. The issues may additionally be tagged with a
difficulty. <code class="docutils literal notranslate"><span class="pre">Difficulty:</span> <span class="pre">Easy</span></code> is suited for people with little Python experience.
<code class="docutils literal notranslate"><span class="pre">Difficulty:</span> <span class="pre">Medium</span></code> and <code class="docutils literal notranslate"><span class="pre">Difficulty:</span> <span class="pre">Hard</span></code> are not trivial to solve and
require more thought and programming experience.</p>
</div>
</div>
<div class="section" id="submitting-a-bug-report">
<span id="id2"></span><h2>Submitting a bug report<a class="headerlink" href="#submitting-a-bug-report" title="Permalink to this headline">¶</a></h2>
<p>If you find a bug in the code or documentation, do not hesitate to submit a
ticket to the
<a class="reference external" href="https://github.com/matplotlib/matplotlib/issues">Issue Tracker</a>. You are
also welcome to post feature requests or pull requests.</p>
<p>If you are reporting a bug, please do your best to include the following:</p>
<ol class="arabic">
<li><p class="first">A short, top-level summary of the bug. In most cases, this should be 1-2
sentences.</p>
</li>
<li><p class="first">A short, self-contained code snippet to reproduce the bug, ideally allowing
a simple copy and paste to reproduce. Please do your best to reduce the code
snippet to the minimum required.</p>
</li>
<li><p class="first">The actual outcome of the code snippet.</p>
</li>
<li><p class="first">The expected outcome of the code snippet.</p>
</li>
<li><p class="first">The Matplotlib version, Python version and platform that you are using. You
can grab the version with the following commands:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">matplotlib</span>
<span class="gp">>>> </span><span class="n">matplotlib</span><span class="o">.</span><span class="n">__version__</span>
<span class="go">'3.4.1'</span>
<span class="gp">>>> </span><span class="kn">import</span> <span class="nn">platform</span>
<span class="gp">>>> </span><span class="n">platform</span><span class="o">.</span><span class="n">python_version</span><span class="p">()</span>
<span class="go">'3.9.2'</span>
</pre></div>
</div>
</li>
</ol>
<p>We have preloaded the issue creation page with a Markdown template that you can
use to organize this information.</p>
<p>Thank you for your help in keeping bug reports complete, targeted and descriptive.</p>
</div>
<div class="section" id="requesting-a-new-feature">
<h2>Requesting a new feature<a class="headerlink" href="#requesting-a-new-feature" title="Permalink to this headline">¶</a></h2>
<p>Please post feature requests to the
<a class="reference external" href="https://github.com/matplotlib/matplotlib/issues">Issue Tracker</a>.</p>
<p>The Matplotlib developers will give feedback on the feature proposal. Since
Matplotlib is an open source project with limited resources, we encourage
users to then also
<a class="reference internal" href="#contributing-code"><span class="std std-ref">participate in the implementation</span></a>.</p>
</div>
<div class="section" id="contributing-code">
<span id="id4"></span><h2>Contributing code<a class="headerlink" href="#contributing-code" title="Permalink to this headline">¶</a></h2>
<div class="section" id="how-to-contribute">
<span id="id5"></span><h3>How to contribute<a class="headerlink" href="#how-to-contribute" title="Permalink to this headline">¶</a></h3>
<p>The preferred way to contribute to Matplotlib is to fork the <a class="reference external" href="https://github.com/matplotlib/matplotlib/">main
repository</a> on GitHub,
then submit a "pull request" (PR).</p>
<p>A brief overview is:</p>
<ol class="arabic">
<li><p class="first"><a class="reference external" href="https://github.com/join">Create an account</a> on GitHub if you do not
already have one.</p>
</li>
<li><p class="first">Fork the <a class="reference external" href="https://github.com/matplotlib/matplotlib">project repository</a>:
click on the 'Fork' button near the top of the page. This creates a copy of
the code under your account on the GitHub server.</p>
</li>
<li><p class="first">Clone this copy to your local disk:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">git</span> <span class="n">clone</span> <span class="n">https</span><span class="p">:</span><span class="o">//</span><span class="n">github</span><span class="o">.</span><span class="n">com</span><span class="o">/<</span><span class="n">YOUR</span> <span class="n">GITHUB</span> <span class="n">USERNAME</span><span class="o">>/</span><span class="n">matplotlib</span><span class="o">.</span><span class="n">git</span>
</pre></div>
</div>
</li>
<li><p class="first">Enter the directory and install the local version of Matplotlib.
See ref`<installing_for_devs>` for instructions</p>
</li>
<li><p class="first">Create a branch to hold your changes:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">git</span> <span class="n">checkout</span> <span class="o">-</span><span class="n">b</span> <span class="n">my</span><span class="o">-</span><span class="n">feature</span> <span class="n">origin</span><span class="o">/</span><span class="n">master</span>
</pre></div>
</div>
<p>and start making changes. Never work in the <code class="docutils literal notranslate"><span class="pre">master</span></code> branch!</p>
</li>
<li><p class="first">Work on this copy, on your computer, using Git to do the version control.
When you're done editing e.g., <code class="docutils literal notranslate"><span class="pre">lib/matplotlib/collections.py</span></code>, do:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">git</span> <span class="n">add</span> <span class="n">lib</span><span class="o">/</span><span class="n">matplotlib</span><span class="o">/</span><span class="n">collections</span><span class="o">.</span><span class="n">py</span>
<span class="n">git</span> <span class="n">commit</span>
</pre></div>
</div>
<p>to record your changes in Git, then push them to GitHub with:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">git</span> <span class="n">push</span> <span class="o">-</span><span class="n">u</span> <span class="n">origin</span> <span class="n">my</span><span class="o">-</span><span class="n">feature</span>
</pre></div>
</div>
</li>
</ol>
<p>Finally, go to the web page of your fork of the Matplotlib repo, and click
'Pull request' to send your changes to the maintainers for review.</p>
<div class="admonition seealso">
<p class="first admonition-title">See also</p>
<ul class="last simple">
<li><a class="reference external" href="https://git-scm.com/documentation">Git documentation</a></li>
<li><a class="reference external" href="https://git-scm.com/book/en/v2/GitHub-Contributing-to-a-Project">Git-Contributing to a Project</a></li>
<li><a class="reference external" href="https://lab.github.com/githubtraining/introduction-to-github">Introduction to GitHub</a></li>
<li><a class="reference internal" href="gitwash/development_workflow.html#development-workflow"><span class="std std-ref">Development workflow</span></a> for best practices for Matplotlib</li>
<li><a class="reference internal" href="gitwash/index.html#using-git"><span class="std std-ref">Working with Matplotlib source code</span></a></li>
</ul>
</div>
</div>
<div class="section" id="contributing-pull-requests">
<h3>Contributing pull requests<a class="headerlink" href="#contributing-pull-requests" title="Permalink to this headline">¶</a></h3>
<p>It is recommended to check that your contribution complies with the following
rules before submitting a pull request:</p>
<ul>
<li><p class="first">If your pull request addresses an issue, please use the title to describe the
issue and mention the issue number in the pull request description to ensure
that a link is created to the original issue.</p>
</li>
<li><p class="first">All public methods should have informative docstrings with sample usage when
appropriate. Use the <a class="reference external" href="https://numpydoc.readthedocs.io/en/latest/format.html">numpy docstring standard</a>.</p>
</li>
<li><p class="first">Formatting should follow the recommendations of <a class="reference external" href="https://www.python.org/dev/peps/pep-0008/">PEP8</a>. You should consider
installing/enabling automatic PEP8 checking in your editor. Part of the test
suite is checking PEP8 compliance, things go smoother if the code is mostly
PEP8 compliant to begin with.</p>
</li>
<li><p class="first">Each high-level plotting function should have a simple example in the
<code class="docutils literal notranslate"><span class="pre">Example</span></code> section of the docstring. This should be as simple as possible
to demonstrate the method. More complex examples should go in the
<code class="docutils literal notranslate"><span class="pre">examples</span></code> tree.</p>
</li>
<li><p class="first">Changes (both new features and bugfixes) should be tested. See <a class="reference internal" href="testing.html#testing"><span class="std std-ref">Testing</span></a>
for more details.</p>
</li>
<li><p class="first">Import the following modules using the standard scipy conventions:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">numpy</span> <span class="k">as</span> <span class="nn">np</span>
<span class="kn">import</span> <span class="nn">numpy.ma</span> <span class="k">as</span> <span class="nn">ma</span>
<span class="kn">import</span> <span class="nn">matplotlib</span> <span class="k">as</span> <span class="nn">mpl</span>
<span class="kn">import</span> <span class="nn">matplotlib.pyplot</span> <span class="k">as</span> <span class="nn">plt</span>
<span class="kn">import</span> <span class="nn">matplotlib.cbook</span> <span class="k">as</span> <span class="nn">cbook</span>
<span class="kn">import</span> <span class="nn">matplotlib.patches</span> <span class="k">as</span> <span class="nn">mpatches</span>
</pre></div>
</div>
<p>In general, Matplotlib modules should <strong>not</strong> import <a class="reference internal" href="../api/matplotlib_configuration_api.html#matplotlib.rcParams" title="matplotlib.rcParams"><code class="xref py py-obj docutils literal notranslate"><span class="pre">rcParams</span></code></a> using <code class="docutils literal notranslate"><span class="pre">from</span>
<span class="pre">matplotlib</span> <span class="pre">import</span> <span class="pre">rcParams</span></code>, but rather access it as <code class="docutils literal notranslate"><span class="pre">mpl.rcParams</span></code>. This
is because some modules are imported very early, before the <a class="reference internal" href="../api/matplotlib_configuration_api.html#matplotlib.rcParams" title="matplotlib.rcParams"><code class="xref py py-obj docutils literal notranslate"><span class="pre">rcParams</span></code></a>
singleton is constructed.</p>
</li>
<li><p class="first">If your change is a major new feature, add an entry to the <code class="docutils literal notranslate"><span class="pre">What's</span> <span class="pre">new</span></code>
section by adding a new file in <code class="docutils literal notranslate"><span class="pre">doc/users/next_whats_new</span></code> (see
<code class="file docutils literal notranslate"><span class="pre">doc/users/next_whats_new/README.rst</span></code> for more information).</p>
</li>
<li><p class="first">If you change the API in a backward-incompatible way, please document it in
<code class="file docutils literal notranslate"><span class="pre">doc/api/next_api_changes/behavior</span></code>, by adding a new file with the
naming convention <code class="docutils literal notranslate"><span class="pre">99999-ABC.rst</span></code> where the pull request number is followed
by the contributor's initials. (see <code class="file docutils literal notranslate"><span class="pre">doc/api/api_changes.rst</span></code> for more
information)</p>
</li>
<li><p class="first">See below for additional points about <a class="reference internal" href="#keyword-argument-processing"><span class="std std-ref">Keyword argument processing</span></a>, if
applicable for your pull request.</p>
</li>
</ul>
<p>In addition, you can check for common programming errors with the following
tools:</p>
<ul>
<li><p class="first">Code with a good unittest coverage (at least 70%, better 100%), check with:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">python</span> <span class="o">-</span><span class="n">m</span> <span class="n">pip</span> <span class="n">install</span> <span class="n">coverage</span>
<span class="n">python</span> <span class="o">-</span><span class="n">m</span> <span class="n">pytest</span> <span class="o">--</span><span class="n">cov</span><span class="o">=</span><span class="n">matplotlib</span> <span class="o">--</span><span class="n">showlocals</span> <span class="o">-</span><span class="n">v</span>
</pre></div>
</div>
</li>
<li><p class="first">No pyflakes warnings, check with:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">python</span> <span class="o">-</span><span class="n">m</span> <span class="n">pip</span> <span class="n">install</span> <span class="n">pyflakes</span>
<span class="n">pyflakes</span> <span class="n">path</span><span class="o">/</span><span class="n">to</span><span class="o">/</span><span class="n">module</span><span class="o">.</span><span class="n">py</span>
</pre></div>
</div>
</li>
</ul>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The current state of the Matplotlib code base is not compliant with all
of those guidelines, but we expect that enforcing those constraints on all
new contributions will move the overall code base quality in the right
direction.</p>
</div>
<div class="admonition seealso">
<p class="first admonition-title">See also</p>
<ul class="last simple">
<li><a class="reference internal" href="#coding-guidelines"><span class="std std-ref">Coding guidelines</span></a></li>
<li><a class="reference internal" href="testing.html#testing"><span class="std std-ref">Testing</span></a></li>
<li><a class="reference internal" href="documenting_mpl.html#documenting-matplotlib"><span class="std std-ref">Writing documentation</span></a></li>
</ul>
</div>
</div>
</div>
<div class="section" id="contributing-documentation">
<span id="id6"></span><h2>Contributing documentation<a class="headerlink" href="#contributing-documentation" title="Permalink to this headline">¶</a></h2>
<p>You as an end-user of Matplotlib can make a valuable contribution because you
more clearly see the potential for improvement than a core developer. For example, you can:</p>
<ul class="simple">
<li>Fix a typo</li>
<li>Clarify a docstring</li>
<li>Write or update an <a class="reference internal" href="../gallery/index.html#gallery"><span class="std std-ref">example plot</span></a></li>
<li>Write or update a comprehensive <a class="reference internal" href="../tutorials/index.html#tutorials"><span class="std std-ref">tutorial</span></a></li>
</ul>
<p>The documentation source files live in the same GitHub repository as the code.
Contributions are proposed and accepted through the pull request process.
For details see <a class="reference internal" href="#how-to-contribute"><span class="std std-ref">How to contribute</span></a>.</p>
<p>If you have trouble getting started, you may instead open an <a class="reference external" href="https://github.com/matplotlib/matplotlib/issues">issue</a>
describing the intended improvement.</p>
<div class="admonition seealso">
<p class="first admonition-title">See also</p>
<ul class="last simple">
<li><a class="reference internal" href="documenting_mpl.html#documenting-matplotlib"><span class="std std-ref">Writing documentation</span></a></li>
</ul>
</div>
</div>
<div class="section" id="other-ways-to-contribute">
<span id="id7"></span><h2>Other ways to contribute<a class="headerlink" href="#other-ways-to-contribute" title="Permalink to this headline">¶</a></h2>
<p>It also helps us if you spread the word: reference the project from your blog
and articles or link to it from your website! If Matplotlib contributes to a
project that leads to a scientific publication, please follow the
<a class="reference internal" href="../citing.html"><span class="doc">Citing Matplotlib</span></a> guidelines.</p>
</div>
<div class="section" id="coding-guidelines">
<span id="id8"></span><h2>Coding guidelines<a class="headerlink" href="#coding-guidelines" title="Permalink to this headline">¶</a></h2>
<div class="section" id="api-changes">
<h3>API changes<a class="headerlink" href="#api-changes" title="Permalink to this headline">¶</a></h3>
<p>Changes to the public API must follow a standard deprecation procedure to
prevent unexpected breaking of code that uses Matplotlib.</p>
<ul class="simple">
<li>Deprecations must be announced via a new file in
a new file in <code class="file docutils literal notranslate"><span class="pre">doc/api/next_api_changes/deprecations/</span></code> with
naming convention <code class="docutils literal notranslate"><span class="pre">99999-ABC.rst</span></code> where <code class="docutils literal notranslate"><span class="pre">99999</span></code> is the pull request
number and <code class="docutils literal notranslate"><span class="pre">ABC</span></code> are the contributor's initials.</li>
<li>Deprecations are targeted at the next point-release (i.e. 3.x.0).</li>
<li>The deprecated API should, to the maximum extent possible, remain fully
functional during the deprecation period. In cases where this is not
possible, the deprecation must never make a given piece of code do something
different than it was before; at least an exception should be raised.</li>
<li>If possible, usage of an deprecated API should emit a
<a class="reference internal" href="../api/_api_api.html#matplotlib._api.deprecation.MatplotlibDeprecationWarning" title="matplotlib._api.deprecation.MatplotlibDeprecationWarning"><code class="xref py py-obj docutils literal notranslate"><span class="pre">MatplotlibDeprecationWarning</span></code></a>. There are a number of helper tools for this:<ul>
<li>Use <code class="docutils literal notranslate"><span class="pre">cbook.warn_deprecated()</span></code> for general deprecation warnings.</li>
<li>Use the decorator <code class="docutils literal notranslate"><span class="pre">@cbook.deprecated</span></code> to deprecate classes, functions,
methods, or properties.</li>
<li>To warn on changes of the function signature, use the decorators
<code class="docutils literal notranslate"><span class="pre">@cbook._delete_parameter</span></code>, <code class="docutils literal notranslate"><span class="pre">@cbook._rename_parameter</span></code>, and
<code class="docutils literal notranslate"><span class="pre">@cbook._make_keyword_only</span></code>.</li>
</ul>
</li>
<li>Deprecated API may be removed two point-releases after they were deprecated.</li>
</ul>
</div>
<div class="section" id="adding-new-api">
<h3>Adding new API<a class="headerlink" href="#adding-new-api" title="Permalink to this headline">¶</a></h3>
<p>Every new function, parameter and attribute that is not explicitly marked as
private (i.e., starts with an underscore) becomes part of Matplotlib's public
API. As discussed above, changing the existing API is cumbersome. Therefore,
take particular care when adding new API:</p>
<ul class="simple">
<li>Mark helper functions and internal attributes as private by prefixing them
with an underscore.</li>
<li>Carefully think about good names for your functions and variables.</li>
<li>Try to adopt patterns and naming conventions from existing parts of the
Matplotlib API.</li>
<li>Consider making as many arguments keyword-only as possible. See also
<a class="reference external" href="https://emptysqua.re/blog/api-evolution-the-right-way/#adding-parameters">API Evolution the Right Way -- Add Parameters Compatibly</a>.</li>
</ul>
</div>
<div class="section" id="new-modules-and-files-installation">
<h3>New modules and files: installation<a class="headerlink" href="#new-modules-and-files-installation" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li>If you have added new files or directories, or reorganized existing
ones, make sure the new files are included in the match patterns in
<code class="file docutils literal notranslate"><span class="pre">MANIFEST.in</span></code>, and/or in <em>package_data</em> in <code class="file docutils literal notranslate"><span class="pre">setup.py</span></code>.</li>
</ul>
</div>
<div class="section" id="c-c-extensions">
<h3>C/C++ extensions<a class="headerlink" href="#c-c-extensions" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li>Extensions may be written in C or C++.</li>
<li>Code style should conform to PEP7 (understanding that PEP7 doesn't
address C++, but most of its admonitions still apply).</li>
<li>Python/C interface code should be kept separate from the core C/C++
code. The interface code should be named <code class="file docutils literal notranslate"><span class="pre">FOO_wrap.cpp</span></code> or
<code class="file docutils literal notranslate"><span class="pre">FOO_wrapper.cpp</span></code>.</li>
<li>Header file documentation (aka docstrings) should be in Numpydoc
format. We don't plan on using automated tools for these
docstrings, and the Numpydoc format is well understood in the
scientific Python community.</li>
</ul>
</div>
<div class="section" id="keyword-argument-processing">
<span id="id10"></span><h3>Keyword argument processing<a class="headerlink" href="#keyword-argument-processing" title="Permalink to this headline">¶</a></h3>
<p>Matplotlib makes extensive use of <code class="docutils literal notranslate"><span class="pre">**kwargs</span></code> for pass-through customizations
from one function to another. A typical example is in <a class="reference internal" href="../api/_as_gen/matplotlib.pyplot.text.html#matplotlib.pyplot.text" title="matplotlib.pyplot.text"><code class="xref py py-obj docutils literal notranslate"><span class="pre">matplotlib.pyplot.text</span></code></a>.
The definition of the pylab text function is a simple pass-through to
<a class="reference internal" href="../api/_as_gen/matplotlib.axes.Axes.text.html#matplotlib.axes.Axes.text" title="matplotlib.axes.Axes.text"><code class="xref py py-obj docutils literal notranslate"><span class="pre">matplotlib.axes.Axes.text</span></code></a>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># in pylab.py</span>
<span class="k">def</span> <span class="nf">text</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="k">return</span> <span class="n">gca</span><span class="p">()</span><span class="o">.</span><span class="n">text</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">)</span>
</pre></div>
</div>
<p><a class="reference internal" href="../api/_as_gen/matplotlib.axes.Axes.text.html#matplotlib.axes.Axes.text" title="matplotlib.axes.Axes.text"><code class="xref py py-obj docutils literal notranslate"><span class="pre">text</span></code></a> in simplified form looks like this, i.e., it just
passes all <code class="docutils literal notranslate"><span class="pre">args</span></code> and <code class="docutils literal notranslate"><span class="pre">kwargs</span></code> on to <code class="docutils literal notranslate"><span class="pre">matplotlib.text.Text.__init__</span></code>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># in axes/_axes.py</span>
<span class="k">def</span> <span class="nf">text</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">,</span> <span class="n">s</span><span class="p">,</span> <span class="n">fontdict</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">withdash</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="n">t</span> <span class="o">=</span> <span class="n">Text</span><span class="p">(</span><span class="n">x</span><span class="o">=</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="o">=</span><span class="n">y</span><span class="p">,</span> <span class="n">text</span><span class="o">=</span><span class="n">s</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">)</span>
</pre></div>
</div>
<p>and <code class="docutils literal notranslate"><span class="pre">matplotlib.text.Text.__init__</span></code> (again with liberties for illustration)
just passes them on to the <a class="reference internal" href="../api/_as_gen/matplotlib.artist.Artist.update.html#matplotlib.artist.Artist.update" title="matplotlib.artist.Artist.update"><code class="xref py py-obj docutils literal notranslate"><span class="pre">matplotlib.artist.Artist.update</span></code></a> method:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># in text.py</span>
<span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">x</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span> <span class="n">y</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span> <span class="n">text</span><span class="o">=</span><span class="s1">''</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">()</span>
<span class="bp">self</span><span class="o">.</span><span class="n">update</span><span class="p">(</span><span class="n">kwargs</span><span class="p">)</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">update</span></code> does the work looking for methods named like
<code class="docutils literal notranslate"><span class="pre">set_property</span></code> if <code class="docutils literal notranslate"><span class="pre">property</span></code> is a keyword argument. i.e., no one
looks at the keywords, they just get passed through the API to the
artist constructor which looks for suitably named methods and calls
them with the value.</p>
<p>As a general rule, the use of <code class="docutils literal notranslate"><span class="pre">**kwargs</span></code> should be reserved for
pass-through keyword arguments, as in the example above. If all the
keyword args are to be used in the function, and not passed
on, use the key/value keyword args in the function definition rather
than the <code class="docutils literal notranslate"><span class="pre">**kwargs</span></code> idiom.</p>
<p>In some cases, you may want to consume some keys in the local
function, and let others pass through. Instead of popping arguments to
use off <code class="docutils literal notranslate"><span class="pre">**kwargs</span></code>, specify them as keyword-only arguments to the local
function. This makes it obvious at a glance which arguments will be
consumed in the function. For example, in
<a class="reference internal" href="../api/_as_gen/matplotlib.axes.Axes.plot.html#matplotlib.axes.Axes.plot" title="matplotlib.axes.Axes.plot"><code class="xref py py-meth docutils literal notranslate"><span class="pre">plot()</span></code></a>, <code class="docutils literal notranslate"><span class="pre">scalex</span></code> and <code class="docutils literal notranslate"><span class="pre">scaley</span></code> are
local arguments and the rest are passed on as
<a class="reference internal" href="../api/_as_gen/matplotlib.lines.Line2D.html#matplotlib.lines.Line2D" title="matplotlib.lines.Line2D"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Line2D()</span></code></a> keyword arguments:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># in axes/_axes.py</span>
<span class="k">def</span> <span class="nf">plot</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="n">scalex</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">scaley</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="n">lines</span> <span class="o">=</span> <span class="p">[]</span>
<span class="k">for</span> <span class="n">line</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">_get_lines</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">add_line</span><span class="p">(</span><span class="n">line</span><span class="p">)</span>
<span class="n">lines</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">line</span><span class="p">)</span>
</pre></div>
</div>
</div>
<div class="section" id="using-logging-for-debug-messages">
<span id="using-logging"></span><h3>Using logging for debug messages<a class="headerlink" href="#using-logging-for-debug-messages" title="Permalink to this headline">¶</a></h3>
<p>Matplotlib uses the standard Python <a class="reference external" href="https://docs.python.org/3/library/logging.html#module-logging" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging</span></code></a> library to write verbose
warnings, information, and debug messages. Please use it! In all those places
you write <a class="reference external" href="https://docs.python.org/3/library/functions.html#print" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">print</span></code></a> calls to do your debugging, try using <a class="reference external" href="https://docs.python.org/3/library/logging.html#logging.debug" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging.debug</span></code></a>
instead!</p>
<p>To include <a class="reference external" href="https://docs.python.org/3/library/logging.html#module-logging" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging</span></code></a> in your module, at the top of the module, you need to
<code class="docutils literal notranslate"><span class="pre">import</span> <span class="pre">logging</span></code>. Then calls in your code like:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">_log</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="vm">__name__</span><span class="p">)</span> <span class="c1"># right after the imports</span>
<span class="c1"># code</span>
<span class="c1"># more code</span>
<span class="n">_log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s1">'Here is some information'</span><span class="p">)</span>
<span class="n">_log</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s1">'Here is some more detailed information'</span><span class="p">)</span>
</pre></div>
</div>
<p>will log to a logger named <code class="docutils literal notranslate"><span class="pre">matplotlib.yourmodulename</span></code>.</p>
<p>If an end-user of Matplotlib sets up <a class="reference external" href="https://docs.python.org/3/library/logging.html#module-logging" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging</span></code></a> to display at levels more
verbose than <code class="docutils literal notranslate"><span class="pre">logging.WARNING</span></code> in their code with the Matplotlib-provided
helper:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">plt</span><span class="o">.</span><span class="n">set_loglevel</span><span class="p">(</span><span class="s2">"debug"</span><span class="p">)</span>
</pre></div>
</div>
<p>or manually with</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">logging</span>
<span class="n">logging</span><span class="o">.</span><span class="n">basicConfig</span><span class="p">(</span><span class="n">level</span><span class="o">=</span><span class="n">logging</span><span class="o">.</span><span class="n">DEBUG</span><span class="p">)</span>
<span class="kn">import</span> <span class="nn">matplotlib.pyplot</span> <span class="k">as</span> <span class="nn">plt</span>
</pre></div>
</div>
<p>Then they will receive messages like:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">DEBUG</span><span class="p">:</span><span class="n">matplotlib</span><span class="o">.</span><span class="n">backends</span><span class="p">:</span><span class="n">backend</span> <span class="n">MacOSX</span> <span class="n">version</span> <span class="n">unknown</span>
<span class="n">DEBUG</span><span class="p">:</span><span class="n">matplotlib</span><span class="o">.</span><span class="n">yourmodulename</span><span class="p">:</span><span class="n">Here</span> <span class="ow">is</span> <span class="n">some</span> <span class="n">information</span>
<span class="n">DEBUG</span><span class="p">:</span><span class="n">matplotlib</span><span class="o">.</span><span class="n">yourmodulename</span><span class="p">:</span><span class="n">Here</span> <span class="ow">is</span> <span class="n">some</span> <span class="n">more</span> <span class="n">detailed</span> <span class="n">information</span>
</pre></div>
</div>
<div class="section" id="which-logging-level-to-use">
<h4>Which logging level to use?<a class="headerlink" href="#which-logging-level-to-use" title="Permalink to this headline">¶</a></h4>
<p>There are five levels at which you can emit messages.</p>
<ul class="simple">
<li><a class="reference external" href="https://docs.python.org/3/library/logging.html#logging.critical" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging.critical</span></code></a> and <a class="reference external" href="https://docs.python.org/3/library/logging.html#logging.error" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging.error</span></code></a> are really only there for errors that
will end the use of the library but not kill the interpreter.</li>
<li><a class="reference external" href="https://docs.python.org/3/library/logging.html#logging.warning" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging.warning</span></code></a> and <a class="reference internal" href="../api/_api_api.html#matplotlib._api.warn_external" title="matplotlib._api.warn_external"><code class="xref py py-obj docutils literal notranslate"><span class="pre">_api.warn_external</span></code></a> are used to warn the user,
see below.</li>
<li><a class="reference external" href="https://docs.python.org/3/library/logging.html#logging.info" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging.info</span></code></a> is for information that the user may want to know if the
program behaves oddly. They are not displayed by default. For instance, if
an object isn't drawn because its position is <code class="docutils literal notranslate"><span class="pre">NaN</span></code>, that can usually
be ignored, but a mystified user could call
<code class="docutils literal notranslate"><span class="pre">logging.basicConfig(level=logging.INFO)</span></code> and get an error message that
says why.</li>
<li><a class="reference external" href="https://docs.python.org/3/library/logging.html#logging.debug" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging.debug</span></code></a> is the least likely to be displayed, and hence can be the
most verbose. "Expected" code paths (e.g., reporting normal intermediate
steps of layouting or rendering) should only log at this level.</li>
</ul>
<p>By default, <a class="reference external" href="https://docs.python.org/3/library/logging.html#module-logging" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging</span></code></a> displays all log messages at levels higher than
<code class="docutils literal notranslate"><span class="pre">logging.WARNING</span></code> to <a class="reference external" href="https://docs.python.org/3/library/sys.html#sys.stderr" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">sys.stderr</span></code></a>.</p>
<p>The <a class="reference external" href="https://docs.python.org/3/howto/logging.html#logging-basic-tutorial">logging tutorial</a> suggests that the difference between <a class="reference external" href="https://docs.python.org/3/library/logging.html#logging.warning" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging.warning</span></code></a>
and <a class="reference internal" href="../api/_api_api.html#matplotlib._api.warn_external" title="matplotlib._api.warn_external"><code class="xref py py-obj docutils literal notranslate"><span class="pre">_api.warn_external</span></code></a> (which uses <a class="reference external" href="https://docs.python.org/3/library/warnings.html#warnings.warn" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">warnings.warn</span></code></a>) is that
<a class="reference internal" href="../api/_api_api.html#matplotlib._api.warn_external" title="matplotlib._api.warn_external"><code class="xref py py-obj docutils literal notranslate"><span class="pre">_api.warn_external</span></code></a> should be used for things the user must change to stop
the warning (typically in the source), whereas <a class="reference external" href="https://docs.python.org/3/library/logging.html#logging.warning" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging.warning</span></code></a> can be more
persistent. Moreover, note that <a class="reference internal" href="../api/_api_api.html#matplotlib._api.warn_external" title="matplotlib._api.warn_external"><code class="xref py py-obj docutils literal notranslate"><span class="pre">_api.warn_external</span></code></a> will by default only
emit a given warning <em>once</em> for each line of user code, whereas
<a class="reference external" href="https://docs.python.org/3/library/logging.html#logging.warning" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">logging.warning</span></code></a> will display the message every time it is called.</p>
<p>By default, <a class="reference external" href="https://docs.python.org/3/library/warnings.html#warnings.warn" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">warnings.warn</span></code></a> displays the line of code that has the <code class="docutils literal notranslate"><span class="pre">warn</span></code>
call. This usually isn't more informative than the warning message itself.
Therefore, Matplotlib uses <a class="reference internal" href="../api/_api_api.html#matplotlib._api.warn_external" title="matplotlib._api.warn_external"><code class="xref py py-obj docutils literal notranslate"><span class="pre">_api.warn_external</span></code></a> which uses <a class="reference external" href="https://docs.python.org/3/library/warnings.html#warnings.warn" title="(in Python v3.9)"><code class="xref py py-obj docutils literal notranslate"><span class="pre">warnings.warn</span></code></a>,
but goes up the stack and displays the first line of code outside of
Matplotlib. For example, for the module:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># in my_matplotlib_module.py</span>
<span class="kn">import</span> <span class="nn">warnings</span>
<span class="k">def</span> <span class="nf">set_range</span><span class="p">(</span><span class="n">bottom</span><span class="p">,</span> <span class="n">top</span><span class="p">):</span>
<span class="k">if</span> <span class="n">bottom</span> <span class="o">==</span> <span class="n">top</span><span class="p">:</span>
<span class="n">warnings</span><span class="o">.</span><span class="n">warn</span><span class="p">(</span><span class="s1">'Attempting to set identical bottom==top'</span><span class="p">)</span>
</pre></div>
</div>
<p>running the script:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">matplotlib</span> <span class="kn">import</span> <span class="n">my_matplotlib_module</span>
<span class="n">my_matplotlib_module</span><span class="o">.</span><span class="n">set_range</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span> <span class="c1">#set range</span>
</pre></div>
</div>
<p>will display:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="ne">UserWarning</span><span class="p">:</span> <span class="n">Attempting</span> <span class="n">to</span> <span class="nb">set</span> <span class="n">identical</span> <span class="n">bottom</span><span class="o">==</span><span class="n">top</span>
<span class="n">warnings</span><span class="o">.</span><span class="n">warn</span><span class="p">(</span><span class="s1">'Attempting to set identical bottom==top'</span><span class="p">)</span>
</pre></div>
</div>
<p>Modifying the module to use <a class="reference internal" href="../api/_api_api.html#matplotlib._api.warn_external" title="matplotlib._api.warn_external"><code class="xref py py-obj docutils literal notranslate"><span class="pre">_api.warn_external</span></code></a>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">matplotlib</span> <span class="kn">import</span> <span class="n">_api</span>
<span class="k">def</span> <span class="nf">set_range</span><span class="p">(</span><span class="n">bottom</span><span class="p">,</span> <span class="n">top</span><span class="p">):</span>
<span class="k">if</span> <span class="n">bottom</span> <span class="o">==</span> <span class="n">top</span><span class="p">:</span>
<span class="n">_api</span><span class="o">.</span><span class="n">warn_external</span><span class="p">(</span><span class="s1">'Attempting to set identical bottom==top'</span><span class="p">)</span>
</pre></div>
</div>
<p>and running the same script will display:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="ne">UserWarning</span><span class="p">:</span> <span class="n">Attempting</span> <span class="n">to</span> <span class="nb">set</span> <span class="n">identical</span> <span class="n">bottom</span><span class="o">==</span><span class="n">top</span>
<span class="n">my_matplotlib_module</span><span class="o">.</span><span class="n">set_range</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span> <span class="c1">#set range</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="writing-examples">
<span id="sample-data"></span><h3>Writing examples<a class="headerlink" href="#writing-examples" title="Permalink to this headline">¶</a></h3>
<p>We have hundreds of examples in subdirectories of <code class="file docutils literal notranslate"><span class="pre">matplotlib/examples</span></code>,
and these are automatically generated when the website is built to show up in
the <a class="reference internal" href="../gallery/index.html#gallery"><span class="std std-ref">examples</span></a> section of the website.</p>
<p>Any sample data that the example uses should be kept small and
distributed with Matplotlib in the
<code class="file docutils literal notranslate"><span class="pre">lib/matplotlib/mpl-data/sample_data/</span></code> directory. Then in your
example code you can load it into a file handle with:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">matplotlib.cbook</span> <span class="k">as</span> <span class="nn">cbook</span>
<span class="n">fh</span> <span class="o">=</span> <span class="n">cbook</span><span class="o">.</span><span class="n">get_sample_data</span><span class="p">(</span><span class="s1">'mydata.dat'</span><span class="p">)</span>
</pre></div>
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