Contributing¶
This project is a community effort, and everyone is welcome to contribute. We follow the Python Software Foundation Code of Conduct in everything we do.
The project is hosted on https://github.com/matplotlib/matplotlib
Submitting a bug report¶
If you find a bug in the code or documentation, do not hesitate to submit a ticket to the Bug Tracker. You are also welcome to post feature requests or pull requests.
If you are reporting a bug, please do your best to include the following:
A short, top-level summary of the bug. In most cases, this should be 1-2 sentences.
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.
The actual outcome of the code snippet.
The expected outcome of the code snippet.
The Matplotlib version, Python version and platform that you are using. You can grab the version with the following commands:
>>> import matplotlib >>> matplotlib.__version__ '1.5.3' >>> import platform >>> platform.python_version() '2.7.12'
We have preloaded the issue creation page with a Markdown template that you can use to organize this information.
Thank you for your help in keeping bug reports complete, targeted and descriptive.
Retrieving and installing the latest version of the code¶
When developing Matplotlib, sources must be downloaded, built, and installed into a local environment on your machine.
Follow the instructions detailed here to set up your environment to build Matplotlib from source.
Warning
When working on Matplotlib sources, having multiple versions installed by different methods into the same environment may not always work as expected.
To work on Matplotlib sources, it is strongly recommended to set up an alternative development environment, using the something like virtual environments in python, or a conda environment.
If you choose to use an already existing environment, and not a clean virtual or conda environment, uninstall the current version of Matplotlib in that environment using the same method used to install it.
If working on Matplotlib documentation only, the above steps are not absolutely necessary.
We use Git for version control and GitHub for hosting our main repository.
You can check out the latest sources with the command (see Set up your fork for more details):
git clone https://github.com/matplotlib/matplotlib.git
and navigate to the matplotlib
directory. If you have the proper privileges,
you can use git@
instead of https://
, which works through the ssh protocol
and might be easier to use if you are using 2-factor authentication.
Building Matplotlib for image comparison tests¶
Matplotlib's test suite makes heavy use of image comparison tests, meaning the result of a plot is compared against a known good result. Unfortunately, different versions of FreeType produce differently formed characters, causing these image comparisons to fail. To make them reproducible, Matplotlib can be built with a special local copy of FreeType. This is recommended for all Matplotlib developers.
Prior to compiling the C-extensions, copy setup.cfg.template
to
setup.cfg
and edit it to contain:
[test]
local_freetype = True
tests = True
or set the MPLLOCALFREETYPE
environmental variable to any true
value. If you have previously built Matplotlib with a different
version of Freetype, you will also need to remove the c/c++ build
products. Do this is to delete the build
folder or git clean
-xfd
. If you are going to be regularly working on Matplotlib,
consider putting
export MPLLOCALFREETYPE=1
in your shell start up files.
Installing Matplotlib in developer mode¶
To install Matplotlib (and compile the C-extensions) run the following command from the top-level directory
python -mpip install -ve .
This installs Matplotlib in 'editable/develop mode', i.e., builds
everything and places the correct link entries in the install
directory so that python will be able to import Matplotlib from the
source directory. Thus, any changes to the *.py
files will be
reflected the next time you import the library. If you change the
C-extension source (which might happen if you change branches) you
will need to run
python setup.py build
or re-run python -mpip install -ve .
.
Alternatively, if you do
python -mpip install -v .
all of the files will be copied to the installation directory however,
you will have to rerun this command every time the source is changed.
Additionally you will need to copy setup.cfg.template
to
setup.cfg
and edit it to contain
[test]
local_freetype = True
tests = True
In either case you can then run the tests to check your work environment is set up properly:
pytest
Note
Additional dependencies for testing: pytest (version 3.6 or later), Ghostscript, Inkscape
See also
Contributing code¶
How to contribute¶
The preferred way to contribute to Matplotlib is to fork the main repository on GitHub, then submit a "pull request" (PR).
The best practices for using GitHub to make PRs to Matplotlib are documented in the Development workflow section.
A brief overview is:
Create an account on GitHub if you do not already have one.
Fork the project repository: 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.
Clone this copy to your local disk:
$ git clone https://github.com/YourLogin/matplotlib.git
Create a branch to hold your changes:
$ git checkout -b my-feature origin/master
and start making changes. Never work in the
master
branch!Work on this copy, on your computer, using Git to do the version control. When you're done editing e.g.,
lib/matplotlib/collections.py
, do:$ git add lib/matplotlib/collections.py $ git commit
to record your changes in Git, then push them to GitHub with:
$ git push -u origin my-feature
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. You may want to consider sending an email to the mailing list for more visibility.
Contributing pull requests¶
It is recommended to check that your contribution complies with the following rules before submitting a pull request:
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.
All public methods should have informative docstrings with sample usage when appropriate. Use the numpy docstring standard.
Formatting should follow the recommendations of PEP8. 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.
Each high-level plotting function should have a simple example in the
Example
section of the docstring. This should be as simple as possible to demonstrate the method. More complex examples should go in theexamples
tree.Changes (both new features and bugfixes) should be tested. See Developer's tips for testing for more details.
Import the following modules using the standard scipy conventions:
import numpy as np import numpy.ma as ma import matplotlib as mpl import matplotlib.pyplot as plt import matplotlib.cbook as cbook import matplotlib.patches as mpatches
If your change is a major new feature, add an entry to the
What's new
section by adding a new file indoc/users/next_whats_new
(seedoc/users/next_whats_new/README.rst
for more information).If you change the API in a backward-incompatible way, please document it in
doc/api/api_changes
, by adding a new file describing your changes (seedoc/api/api_changes/README.rst
for more information)See below for additional points about Keyword argument processing, if applicable for your pull request.
In addition, you can check for common programming errors with the following tools:
Code with a good unittest coverage (at least 70%, better 100%), check with:
python -mpip install coverage pytest --cov=matplotlib --showlocals -v
No pyflakes warnings, check with:
python -mpip install pyflakes pyflakes path/to/module.py
Note
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.
Issues for New Contributors¶
New contributors should look for the following tags when looking for issues. We strongly recommend that new contributors tackle issues labeled good first issue as they are easy, well documented issues, that do not require an understanding of the different submodules of Matplotlib. This helps the contributor become familiar with the contribution workflow, and for the core devs to become acquainted with the contributor; besides which, we frequently underestimate how easy an issue is to solve!
Contributing documentation¶
Code is not the only way to contribute to Matplotlib. For instance, documentation is also a very important part of the project and often doesn't get as much attention as it deserves. If you find a typo in the documentation, or have made improvements, do not hesitate to send an email to the mailing list or submit a GitHub pull request. To make a pull request, refer to the guidelines outlined in How to contribute.
Full documentation can be found under the doc/
, tutorials/
,
and examples/
directories.
See also
Other ways to contribute¶
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 Citing Matplotlib guidelines.
Coding guidelines¶
API changes¶
Changes to the public API must follow a standard deprecation procedure to prevent unexpected breaking of code that uses Matplotlib.
- Deprecations must be announced via an entry in
doc/api/next_api_changes
. - Deprecations are targeted at the next point-release (i.e. 3.x.0).
- 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.
- If possible, usage of an deprecated API should emit a
MatplotlibDeprecationWarning
. There are a number of helper tools for this:- Use
cbook.warn_deprecated()
for general deprecation warnings. - Use the decorator
@cbook.deprecated
to deprecate classes, functions, methods, or properties. - To warn on changes of the function signature, use the decorators
@cbook._delete_parameter
,@cbook._rename_parameter
, and@cbook._make_keyword_only
.
- Use
- Deprecated API may be removed two point-releases after they were deprecated.
Adding new API¶
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:
- Mark helper functions and internal attributes as private by prefixing them with an underscore.
- Carefully think about good names for your functions and variables.
- Try to adopt patterns and naming conventions from existing parts of the Matplotlib API.
- Consider making as many arguments keyword-only as possible. See also API Evolution the Right Way -- Add Parameters Compatibly.
New modules and files: installation¶
- If you have added new files or directories, or reorganized existing
ones, make sure the new files are included in the match patterns in
MANIFEST.in
, and/or inpackage_data
insetup.py
.
C/C++ extensions¶
- Extensions may be written in C or C++.
- Code style should conform to PEP7 (understanding that PEP7 doesn't address C++, but most of its admonitions still apply).
- Python/C interface code should be kept separate from the core C/C++
code. The interface code should be named
FOO_wrap.cpp
orFOO_wrapper.cpp
. - 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.
Keyword argument processing¶
Matplotlib makes extensive use of **kwargs
for pass-through
customizations from one function to another. A typical example is in
matplotlib.pyplot.text()
. The definition of the pylab text
function is a simple pass-through to
matplotlib.axes.Axes.text()
:
# in pylab.py
def text(*args, **kwargs):
ret = gca().text(*args, **kwargs)
draw_if_interactive()
return ret
text()
in simplified form looks like this,
i.e., it just passes all args
and kwargs
on to
matplotlib.text.Text.__init__()
:
# in axes/_axes.py
def text(self, x, y, s, fontdict=None, withdash=False, **kwargs):
t = Text(x=x, y=y, text=s, **kwargs)
and __init__()
(again with liberties for
illustration) just passes them on to the
matplotlib.artist.Artist.update()
method:
# in text.py
def __init__(self, x=0, y=0, text='', **kwargs):
Artist.__init__(self)
self.update(kwargs)
update
does the work looking for methods named like
set_property
if property
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.
As a general rule, the use of **kwargs
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 **kwargs
idiom.
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 **kwargs
, 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
plot()
, scalex
and scaley
are
local arguments and the rest are passed on as
Line2D()
keyword arguments:
# in axes/_axes.py
def plot(self, *args, scalex=True, scaley=True, **kwargs):
lines = []
for line in self._get_lines(*args, **kwargs):
self.add_line(line)
lines.append(line)
Using logging for debug messages¶
Matplotlib uses the standard python logging
library to write verbose
warnings, information, and
debug messages. Please use it! In all those places you write print()
statements to do your debugging, try using log.debug()
instead!
To include logging
in your module, at the top of the module, you need to
import logging
. Then calls in your code like:
_log = logging.getLogger(__name__) # right after the imports
# code
# more code
_log.info('Here is some information')
_log.debug('Here is some more detailed information')
will log to a logger named matplotlib.yourmodulename
.
If an end-user of Matplotlib sets up logging
to display at levels
more verbose than logger.WARNING
in their code with the Matplotlib-provided
helper:
plt.set_loglevel("debug")
or manually with
import logging
logging.basicConfig(level=logging.DEBUG)
import matplotlib.pyplot as plt
Then they will receive messages like:
DEBUG:matplotlib.backends:backend MacOSX version unknown
DEBUG:matplotlib.yourmodulename:Here is some information
DEBUG:matplotlib.yourmodulename:Here is some more detailed information
Which logging level to use?¶
There are five levels at which you can emit messages.
logging.critical
andlogging.error
are really only there for errors that will end the use of the library but not kill the interpreter.logging.warning
andcbook._warn_external
are used to warn the user, see below.logging.info
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 isNaN
, that can usually be ignored, but a mystified user could calllogging.basicConfig(level=logging.INFO)
and get an error message that says why.logging.debug
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.
By default, logging
displays all log messages at levels higher than
logging.WARNING
to sys.stderr
.
The logging tutorial suggests that the difference
between logging.warning
and cbook._warn_external
(which uses
warnings.warn
) is that cbook._warn_external
should be used for things the
user must change to stop the warning (typically in the source), whereas
logging.warning
can be more persistent. Moreover, note that
cbook._warn_external
will by default only emit a given warning once for
each line of user code, whereas logging.warning
will display the message
every time it is called.
By default, warnings.warn
displays the line of code that has the warn
call.
This usually isn't more informative than the warning message itself. Therefore,
Matplotlib uses cbook._warn_external
which uses warnings.warn
, but goes
up the stack and displays the first line of code outside of Matplotlib.
For example, for the module:
# in my_matplotlib_module.py
import warnings
def set_range(bottom, top):
if bottom == top:
warnings.warn('Attempting to set identical bottom==top')
running the script:
from matplotlib import my_matplotlib_module
my_matplotlib_module.set_range(0, 0) #set range
will display:
UserWarning: Attempting to set identical bottom==top
warnings.warn('Attempting to set identical bottom==top')
Modifying the module to use cbook._warn_external
:
from matplotlib import cbook
def set_range(bottom, top):
if bottom == top:
cbook._warn_external('Attempting to set identical bottom==top')
and running the same script will display:
UserWarning: Attempting to set identical bottom==top
my_matplotlib_module.set_range(0, 0) #set range
Writing examples¶
We have hundreds of examples in subdirectories of
matplotlib/examples
, and these are automatically generated
when the website is built to show up in the examples
section of the website.
Any sample data that the example uses should be kept small and
distributed with Matplotlib in the
lib/matplotlib/mpl-data/sample_data/
directory. Then in your
example code you can load it into a file handle with:
import matplotlib.cbook as cbook
fh = cbook.get_sample_data('mydata.dat')