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<h2>Contributor incubator<aclass="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 <aclass="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>
<sectionid="issues-for-new-contributors">
<spanid="new-contributors"></span><h3>Issues for new contributors<aclass="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
<aclass="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. <codeclass="docutils literal notranslate"><spanclass="pre">Difficulty:</span><spanclass="pre">Easy</span></code> is suited for people with little Python experience.
<codeclass="docutils literal notranslate"><spanclass="pre">Difficulty:</span><spanclass="pre">Medium</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">Difficulty:</span><spanclass="pre">Hard</span></code> are not trivial to solve and
require more thought and programming experience.</p>
</section>
</section>
<sectionid="submitting-a-bug-report">
<spanid="id2"></span><h2>Submitting a bug report<aclass="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
<aclass="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>
<olclass="arabic">
<li><p>A short, top-level summary of the bug. In most cases, this should be 1-2
sentences.</p></li>
<li><p>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>The actual outcome of the code snippet.</p></li>
<li><p>The expected outcome of the code snippet.</p></li>
<li><p>The Matplotlib version, Python version and platform that you are using. You
can grab the version with the following commands:</p>
<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>
</section>
<sectionid="requesting-a-new-feature">
<spanid="request-a-new-feature"></span><h2>Requesting a new feature<aclass="headerlink" href="#requesting-a-new-feature" title="Permalink to this headline">#</a></h2>
<li><p>Enter the directory and install the local version of Matplotlib.
See <aclass="reference internal" href="development_setup.html#installing-for-devs"><spanclass="std std-ref">Setting up Matplotlib for development</span></a> for instructions</p></li>
<li><p><aclass="reference external" href="https://git-scm.com/book/en/v2/GitHub-Contributing-to-a-Project">Git-Contributing to a Project</a></p></li>
<li><p><aclass="reference external" href="https://lab.github.com/githubtraining/introduction-to-github">Introduction to GitHub</a></p></li>
<li><p><aclass="reference internal" href="gitwash/development_workflow.html#development-workflow"><spanclass="std std-ref">Development workflow</span></a> for best practices for Matplotlib</p></li>
<li><p><aclass="reference internal" href="gitwash/index.html#using-git"><spanclass="std std-ref">Working with Matplotlib source code</span></a></p></li>
</ul>
</div>
</section>
<sectionid="contributing-pull-requests">
<h3>Contributing pull requests<aclass="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>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>All public methods should have informative docstrings with sample usage when
appropriate. Use the <aclass="reference external" href="https://numpydoc.readthedocs.io/en/latest/format.html">numpy docstring standard</a>.</p></li>
<li><p>Formatting should follow the recommendations of <aclass="reference external" href="https://www.python.org/dev/peps/pep-0008/">PEP8</a>, as enforced by
<aclass="reference external" href="https://flake8.pycqa.org/">flake8</a>. You can check flake8 compliance from the command line with</p>
<p>or your editor may provide integration with it. Note that Matplotlib
intentionally does not use the <aclass="reference external" href="https://black.readthedocs.io/">black</a> auto-formatter (<aclass="reference external" href="https://github.com/matplotlib/matplotlib/issues/18796">1</a>), in particular due
to its unability to understand the semantics of mathematical expressions
<p>In general, Matplotlib modules should <strong>not</strong> import <aclass="reference internal" href="../api/matplotlib_configuration_api.html#matplotlib.rcParams" title="matplotlib.rcParams"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">rcParams</span></code></a> using <codeclass="docutils literal notranslate"><spanclass="pre">from</span>
<spanclass="pre">matplotlib</span><spanclass="pre">import</span><spanclass="pre">rcParams</span></code>, but rather access it as <codeclass="docutils literal notranslate"><spanclass="pre">mpl.rcParams</span></code>. This
is because some modules are imported very early, before the <aclass="reference internal" href="../api/matplotlib_configuration_api.html#matplotlib.rcParams" title="matplotlib.rcParams"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">rcParams</span></code></a>
singleton is constructed.</p>
</li>
<li><p>If your change is a major new feature, add an entry to the <codeclass="docutils literal notranslate"><spanclass="pre">What's</span><spanclass="pre">new</span></code>
section by adding a new file in <codeclass="docutils literal notranslate"><spanclass="pre">doc/users/next_whats_new</span></code> (see
<codeclass="file docutils literal notranslate"><spanclass="pre">doc/users/next_whats_new/README.rst</span></code> for more information).</p></li>
<li><p>If you change the API in a backward-incompatible way, please document it in
<codeclass="file docutils literal notranslate"><spanclass="pre">doc/api/next_api_changes/behavior</span></code>, by adding a new file with the
naming convention <codeclass="docutils literal notranslate"><spanclass="pre">99999-ABC.rst</span></code> where the pull request number is followed
by the contributor's initials. (see <codeclass="file docutils literal notranslate"><spanclass="pre">doc/api/api_changes.rst</span></code> for more
information)</p></li>
<li><p>See below for additional points about <aclass="reference internal" href="#keyword-argument-processing"><spanclass="std std-ref">Keyword argument processing</span></a>, if
applicable for your pull request.</p></li>
</ul>
<divclass="admonition note">
<pclass="admonition-title">Note</p>
<p>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
<spanid="id9"></span><h2>Contributing documentation<aclass="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>
<ulclass="simple">
<li><p>Fix a typo</p></li>
<li><p>Clarify a docstring</p></li>
<li><p>Write or update an <aclass="reference internal" href="../gallery/index.html#gallery"><spanclass="std std-ref">example plot</span></a></p></li>
<li><p>Write or update a comprehensive <aclass="reference internal" href="../tutorials/index.html#tutorials"><spanclass="std std-ref">tutorial</span></a></p></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 <aclass="reference internal" href="#how-to-contribute"><spanclass="std std-ref">How to contribute</span></a>.</p>
<p>If you have trouble getting started, you may instead open an <aclass="reference external" href="https://github.com/matplotlib/matplotlib/issues">issue</a>
<spanid="id11"></span><h2>Coding guidelines<aclass="headerlink" href="#coding-guidelines" title="Permalink to this headline">#</a></h2>
<sectionid="api-changes">
<h3>API changes<aclass="headerlink" href="#api-changes" title="Permalink to this headline">#</a></h3>
<p>API consistency and stability are of great value. Therefore, API changes
(e.g. signature changes, behavior changes, removals) will only be conducted
if the added benefit is worth the user effort for adapting.</p>
<p>API changes in Matplotlib have to be performed following the deprecation process
below, except in very rare circumstances as deemed necessary by the development team.
This ensures that users are notified before the change will take effect and thus
prevents unexpected breaking of code.</p>
<sectionid="rules">
<h4>Rules<aclass="headerlink" href="#rules" title="Permalink to this headline">#</a></h4>
<ulclass="simple">
<li><p>Deprecations are targeted at the next point.release (e.g. 3.x)</p></li>
<li><p>Deprecated API is generally removed two two point-releases after introduction
of the deprecation. Longer deprecations can be imposed by core developers on
a case-by-case basis to give more time for the transition</p></li>
<li><p>The old API must remain fully functional during the deprecation period</p></li>
<li><p>If alternatives to the deprecated API exist, they should be available
during the deprecation period</p></li>
<li><p>If in doubt, decisions about API changes are finally made by the
API consistency lead developer</p></li>
</ul>
</section>
<sectionid="introducing">
<h4>Introducing<aclass="headerlink" href="#introducing" title="Permalink to this headline">#</a></h4>
<olclass="arabic">
<li><p>Announce the deprecation in a new file
<codeclass="file docutils literal notranslate"><spanclass="pre">doc/api/next_api_changes/deprecations/99999-ABC.rst</span></code> where <codeclass="docutils literal notranslate"><spanclass="pre">99999</span></code>
is the pull request number and <codeclass="docutils literal notranslate"><spanclass="pre">ABC</span></code> are the contributor's initials.</p></li>
<li><p>If possible, issue a <aclass="reference internal" href="../api/_api_api.html#matplotlib._api.deprecation.MatplotlibDeprecationWarning" title="matplotlib._api.deprecation.MatplotlibDeprecationWarning"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">MatplotlibDeprecationWarning</span></code></a> when the deprecated
API is used. There are a number of helper tools for this:</p>
<ulclass="simple">
<li><p>Use <codeclass="docutils literal notranslate"><spanclass="pre">_api.warn_deprecated()</span></code> for general deprecation warnings</p></li>
<li><p>Use the decorator <codeclass="docutils literal notranslate"><spanclass="pre">@_api.deprecated</span></code> to deprecate classes, functions,
methods, or properties</p></li>
<li><p>To warn on changes of the function signature, use the decorators
<codeclass="docutils literal notranslate"><spanclass="pre">@_api.delete_parameter</span></code>, <codeclass="docutils literal notranslate"><spanclass="pre">@_api.rename_parameter</span></code>, and
<p>All these helpers take a first parameter <em>since</em>, which should be set to
the next point release, e.g. "3.x".</p>
<p>You can use standard rst cross references in <em>alternative</em>.</p>
</li>
</ol>
</section>
<sectionid="expiring">
<h4>Expiring<aclass="headerlink" href="#expiring" title="Permalink to this headline">#</a></h4>
<olclass="arabic simple">
<li><p>Announce the API changes in a new file
<codeclass="file docutils literal notranslate"><spanclass="pre">doc/api/next_api_changes/[kind]/99999-ABC.rst</span></code> where <codeclass="docutils literal notranslate"><spanclass="pre">99999</span></code>
is the pull request number and <codeclass="docutils literal notranslate"><spanclass="pre">ABC</span></code> are the contributor's initials, and
<codeclass="docutils literal notranslate"><spanclass="pre">[kind]</span></code> is one of the folders <codeclass="file docutils literal notranslate"><spanclass="pre">behavior</span></code>, <codeclass="file docutils literal notranslate"><spanclass="pre">development</span></code>,
<codeclass="file docutils literal notranslate"><spanclass="pre">removals</span></code>. See <codeclass="file docutils literal notranslate"><spanclass="pre">doc/api/next_api_changes/README.rst</span></code> for more
information. For the content, you can usually copy the deprecation notice
and adapt it slightly.</p></li>
<li><p>Change the code functionality and remove any related deprecation warnings.</p></li>
</ol>
</section>
</section>
<sectionid="adding-new-api">
<h3>Adding new API<aclass="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>
<ulclass="simple">
<li><p>Mark helper functions and internal attributes as private by prefixing them
with an underscore.</p></li>
<li><p>Carefully think about good names for your functions and variables.</p></li>
<li><p>Try to adopt patterns and naming conventions from existing parts of the
Matplotlib API.</p></li>
<li><p>Consider making as many arguments keyword-only as possible. See also
<aclass="reference external" href="https://emptysqua.re/blog/api-evolution-the-right-way/#adding-parameters">API Evolution the Right Way -- Add Parameters Compatibly</a>.</p>
</li>
</ul>
</section>
<sectionid="new-modules-and-files-installation">
<h3>New modules and files: installation<aclass="headerlink" href="#new-modules-and-files-installation" title="Permalink to this headline">#</a></h3>
<ulclass="simple">
<li><p>If you have added new files or directories, or reorganized existing
ones, make sure the new files are included in the match patterns in
in <em>package_data</em> in <codeclass="file docutils literal notranslate"><spanclass="pre">setupext.py</span></code>.</p></li>
</ul>
</section>
<sectionid="c-c-extensions">
<h3>C/C++ extensions<aclass="headerlink" href="#c-c-extensions" title="Permalink to this headline">#</a></h3>
<ulclass="simple">
<li><p>Extensions may be written in C or C++.</p></li>
<li><p>Code style should conform to PEP7 (understanding that PEP7 doesn't
address C++, but most of its admonitions still apply).</p></li>
<li><p>Python/C interface code should be kept separate from the core C/C++
code. The interface code should be named <codeclass="file docutils literal notranslate"><spanclass="pre">FOO_wrap.cpp</span></code> or
<li><p>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.</p></li>
<li><p>C/C++ code in the <codeclass="file docutils literal notranslate"><spanclass="pre">extern/</span></code> directory is vendored, and should be kept
close to upstream whenever possible. It can be modified to fix bugs or
implement new features only if the required changes cannot be made elsewhere
in the codebase. In particular, avoid making style fixes to it.</p></li>
</ul>
</section>
<sectionid="keyword-argument-processing">
<spanid="id13"></span><h3>Keyword argument processing<aclass="headerlink" href="#keyword-argument-processing" title="Permalink to this headline">#</a></h3>
<p>Matplotlib makes extensive use of <codeclass="docutils literal notranslate"><spanclass="pre">**kwargs</span></code> for pass-through customizations
from one function to another. A typical example is
<aclass="reference internal" href="../api/_as_gen/matplotlib.axes.Axes.text.html#matplotlib.axes.Axes.text" title="matplotlib.axes.Axes.text"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">text</span></code></a>. The definition of <aclass="reference internal" href="../api/_as_gen/matplotlib.pyplot.text.html#matplotlib.pyplot.text" title="matplotlib.pyplot.text"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">matplotlib.pyplot.text</span></code></a> is a
<p><aclass="reference internal" href="../api/_as_gen/matplotlib.axes.Axes.text.html#matplotlib.axes.Axes.text" title="matplotlib.axes.Axes.text"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">matplotlib.axes.Axes.text</span></code></a> (simplified for illustration) just
passes all <codeclass="docutils literal notranslate"><spanclass="pre">args</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">kwargs</span></code> on to <codeclass="docutils literal notranslate"><spanclass="pre">matplotlib.text.Text.__init__</span></code>:</p>
<divclass="highlight-default notranslate"><divclass="highlight"><pre><span></span><spanclass="c1"># in axes/_axes.py</span>
just passes them on to the <aclass="reference internal" href="../api/_as_gen/matplotlib.artist.Artist.update.html#matplotlib.artist.Artist.update" title="matplotlib.artist.Artist.update"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">matplotlib.artist.Artist.update</span></code></a> method:</p>
<divclass="highlight-default notranslate"><divclass="highlight"><pre><span></span><spanclass="c1"># in text.py</span>
<p><codeclass="docutils literal notranslate"><spanclass="pre">update</span></code> does the work looking for methods named like
<codeclass="docutils literal notranslate"><spanclass="pre">set_property</span></code> if <codeclass="docutils literal notranslate"><spanclass="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 <codeclass="docutils literal notranslate"><spanclass="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 <codeclass="docutils literal notranslate"><spanclass="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 <codeclass="docutils literal notranslate"><spanclass="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
<aclass="reference internal" href="../api/_as_gen/matplotlib.axes.Axes.plot.html#matplotlib.axes.Axes.plot" title="matplotlib.axes.Axes.plot"><codeclass="xref py py-meth docutils literal notranslate"><spanclass="pre">plot()</span></code></a>, <codeclass="docutils literal notranslate"><spanclass="pre">scalex</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">scaley</span></code> are
<spanid="using-logging"></span><h3>Using logging for debug messages<aclass="headerlink" href="#using-logging-for-debug-messages" title="Permalink to this headline">#</a></h3>
<p>Matplotlib uses the standard Python <aclass="reference external" href="https://docs.python.org/3/library/logging.html#module-logging" title="(in Python v3.10)"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">logging</span></code></a> library to write verbose
warnings, information, and debug messages. Please use it! In all those places
you write <aclass="reference external" href="https://docs.python.org/3/library/functions.html#print" title="(in Python v3.10)"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">print</span></code></a> calls to do your debugging, try using <aclass="reference external" href="https://docs.python.org/3/library/logging.html#logging.debug" title="(in Python v3.10)"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">logging.debug</span></code></a>
instead!</p>
<p>To include <aclass="reference external" href="https://docs.python.org/3/library/logging.html#module-logging" title="(in Python v3.10)"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">logging</span></code></a> in your module, at the top of the module, you need to
<codeclass="docutils literal notranslate"><spanclass="pre">import</span><spanclass="pre">logging</span></code>. Then calls in your code like:</p>
<divclass="highlight-default notranslate"><divclass="highlight"><pre><span></span><spanclass="n">_log</span><spanclass="o">=</span><spanclass="n">logging</span><spanclass="o">.</span><spanclass="n">getLogger</span><spanclass="p">(</span><spanclass="vm">__name__</span><spanclass="p">)</span><spanclass="c1"># right after the imports</span>
<spanclass="c1"># code</span>
<spanclass="c1"># more code</span>
<spanclass="n">_log</span><spanclass="o">.</span><spanclass="n">info</span><spanclass="p">(</span><spanclass="s1">'Here is some information'</span><spanclass="p">)</span>
<spanclass="n">_log</span><spanclass="o">.</span><spanclass="n">debug</span><spanclass="p">(</span><spanclass="s1">'Here is some more detailed information'</span><spanclass="p">)</span>
</pre></div>
</div>
<p>will log to a logger named <codeclass="docutils literal notranslate"><spanclass="pre">matplotlib.yourmodulename</span></code>.</p>
<p>If an end-user of Matplotlib sets up <aclass="reference external" href="https://docs.python.org/3/library/logging.html#module-logging" title="(in Python v3.10)"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">logging</span></code></a> to display at levels more
verbose than <codeclass="docutils literal notranslate"><spanclass="pre">logging.WARNING</span></code> in their code with the Matplotlib-provided
<divclass="highlight-none notranslate"><divclass="highlight"><pre><span></span>DEBUG:matplotlib.backends:backend MacOSX version unknown
DEBUG:matplotlib.yourmodulename:Here is some information
DEBUG:matplotlib.yourmodulename:Here is some more detailed information
</pre></div>
</div>
<sectionid="which-logging-level-to-use">
<h4>Which logging level to use?<aclass="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>
<ulclass="simple">
<li><p><aclass="reference external" href="https://docs.python.org/3/library/logging.html#logging.critical" title="(in Python v3.10)"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">logging.critical</span></code></a> and <aclass="reference external" href="https://docs.python.org/3/library/logging.html#logging.error" title="(in Python v3.10)"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="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.</p></li>
<li><p><aclass="reference external" href="https://docs.python.org/3/library/logging.html#logging.warning" title="(in Python v3.10)"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">logging.warning</span></code></a> and <aclass="reference internal" href="../api/_api_api.html#matplotlib._api.warn_external" title="matplotlib._api.warn_external"><codeclass="xref py py-obj docutils literal notranslate"><spanclass="pre">_api.warn_external</span></code></a> are used to warn the user,