Documenting matplotlib

Getting started

The documentation for matplotlib is generated from ReStructured Text using the Sphinx documentation generation tool. Sphinx-0.4 or later is required. Currently this means we need to install from the svn repository by doing:

svn co http://svn.python.org/projects/doctools/trunk sphinx
cd sphinx
python setup.py install

The documentation sources are found in the doc/ directory in the trunk. To build the users guide in html format, cd into doc/ and do:

python make.py html

or:

./make.py html

you can also pass a latex flag to make.py to build a pdf, or pass no arguments to build everything.

The output produced by Sphinx can be configured by editing the conf.py file located in the doc/.

Organization of matplotlib’s documentation

The actual ReStructured Text files are kept in doc/users, doc/devel, doc/api and doc/faq. The main entry point is doc/index.rst, which pulls in the index.rst file for the users guide, developers guide, api reference, and faqs. The documentation suite is built as a single document in order to make the most effective use of cross referencing, we want to make navigating the Matplotlib documentation as easy as possible.

Additional files can be added to the various guides by including their base file name (the .rst extension is not necessary) in the table of contents. It is also possible to include other documents through the use of an include statement, such as:

.. include:: ../../TODO

Formatting

The Sphinx website contains plenty of documentation concerning ReST markup and working with Sphinx in general. Here are a few additional things to keep in mind:

  • Please familiarize yourself with the Sphinx directives for inline markup. Matplotlib’s documentation makes heavy use of cross-referencing and other semantic markup. For example, when referring to external files, use the :file: directive.

  • Function arguments and keywords should be referred to using the emphasis role. This will keep matplotlib’s documentation consistant with Python’s documentation:

    Here is a description of *argument*

    Please do not use the default role:

    Please do not describe `argument` like this.

    nor the literal role:

    Please do not describe ``argument`` like this.
  • Sphinx does not support tables with column- or row-spanning cells for latex output. Such tables can not be used when documenting matplotlib.

  • Mathematical expressions can be rendered as png images in html, and in the usual way by latex. For example:

    :math:`\sin(x_n^2)` yields: , and:

    .. math::
    
      \int_{-\infty}^{\infty}\frac{e^{i\phi}}{1+x^2\frac{e^{i\phi}}{1+x^2}}

    yields:

  • Interactive IPython sessions can be illustrated in the documentation using the following directive:

    .. sourcecode:: ipython
    
      In [69]: lines = plot([1,2,3])

    which would yield:

    In [69]: lines = plot([1,2,3])
    
  • Footnotes [1] can be added using [#]_, followed later by:

    .. rubric:: Footnotes
    
    .. [#]

    Footnotes

    [1]

    For example.

  • Use the note and warning directives, sparingly, to draw attention to important comments:

    .. note::
       Here is a note

    yields:

    Note

    here is a note

    also:

    Warning

    here is a warning

  • Use the deprecated directive when appropriate:

    .. deprecated:: 0.98
       This feature is obsolete, use something else.

    yields:

    Deprecated in version 0.98: This feature is obsolete, use something else.

  • Use the versionadded and versionchanged directives, which have similar syntax to the deprecated role:

    .. versionadded:: 0.98
       The transforms have been completely revamped.

    New in version 0.98: The transforms have been completely revamped.

  • Use the seealso directive, for example:

    .. seealso::
    
       Using ReST :ref:`emacs-helpers`:
          One example
    
       A bit about :ref:`referring-to-mpl-docs`:
          One more

    yields:

    See also

    Using ResT Emacs helpers:

    One example

    A bit about Referring to mpl documents:

    One more

  • Please keep the Glossary in mind when writing documentation. You can create a references to a term in the glossary with the :term: role.

  • The autodoc extension will handle index entries for the API, but additional entries in the index need to be explicitly added.

Docstrings

In addition to the aforementioned formatting suggestions:

  • Please limit the text width of docstrings to 70 characters.

  • Keyword arguments should be described using a definition list.

    Note

    matplotlib makes extensive use of keyword arguments as pass-through arguments, there are a many cases where a table is used in place of a definition list for autogenerated sections of docstrings.

Figures

Dynamically generated figures

The top level doc dir has a folder called pyplots in which you should include any pyplot plotting scripts that you want to generate figures for the documentation. It is not necessary to explicitly save the figure in the script, this will be done automatically at build time to insure that the code that is included runs and produces the advertised figure. Several figures will be saved with the same basnename as the filename when the documentation is generated (low and high res PNGs, a PDF). Matplotlib includes a Sphinx extension (sphinxext/plot_directive.py) for generating the images from the python script and including either a png copy for html or a pdf for latex:

.. plot:: pyplot_simple.py
   :include-source:

The :scale: directive rescales the image to some percentage of the original size, though we don’t recommend using this in most cases since it is probably better to choose the correct figure size and dpi in mpl and let it handle the scaling. :include-source: will present the contents of the file, marked up as source code.

Static figures

Any figures that rely on optional system configurations need to be handled a little differently. These figures are not to be generated during the documentation build, in order to keep the prerequisites to the documentation effort as low as possible. Please run the doc/pyplots/make.py script when adding such figures, and commit the script and the images to svn. Please also add a line to the README in doc/pyplots for any additional requirements necessary to generate a new figure. Once these steps have been taken, these figures can be included in the usual way:

.. plot:: tex_unicode_demo.py
   :include-source

Referring to mpl documents

In the documentation, you may want to include to a document in the matplotlib src, e.g. a license file, an image file from mpl-data, or an example. When you include these files, include them using a symbolic link from the documentation parent directory. This way, if we relocate the mpl documentation directory, all of the internal pointers to files will not have to change, just the top level symlinks. For example, In the top level doc directory we have symlinks pointing to the mpl examples and mpl-data:

home:~/mpl/doc2> ls -l mpl_*
mpl_data -> ../lib/matplotlib/mpl-data
mpl_examples -> ../examples

In the users subdirectory, if I want to refer to a file in the mpl-data directory, I use the symlink directory. For example, from customizing.rst:

.. literalinclude:: ../mpl_data/matplotlibrc

Internal section references

To maximize internal consistency in section labeling and references, use hypen separated, descriptive labels for section references, eg:

.. _howto-webapp:

and refer to it using the standard reference syntax:

See :ref:`howto-webapp`

Keep in mind that we may want to reorganize the contents later, so let’s avoid top level names in references like user or devel or faq unless necesssary, because for example the FAQ “what is a backend?” could later become part of the users guide, so the label:

.. _what-is-a-backend

is better than:

.. _faq-backend

In addition, since underscores are widely used by Sphinx itself, let’s prefer hyphens to separate words.

Section names, etc

For everything but top level chapters, please use Upper lower for section titles, eg Possible hangups rather than Possible Hangups

Inheritance diagrams

Class inheritance diagrams can be generated with the inheritance-diagram directive. To use it, you provide the directive with a number of class or module names (separated by whitespace). If a module name is provided, all classes in that module will be used. All of the ancestors of these classes will be included in the inheritance diagram.

A single option is available: parts controls how many of parts in the path to the class are shown. For example, if parts == 1, the class matplotlib.patches.Patch is shown as Patch. If parts == 2, it is shown as patches.Patch. If parts == 0, the full path is shown.

Example:

.. inheritance-diagram:: matplotlib.patches matplotlib.lines matplotlib.text
   :parts: 2

Emacs helpers

There is an emacs mode rst.el which automates many important ReST tasks like building and updateing table-of-contents, and promoting or demoting section headings. Here is the basic .emacs configuration:

(require 'rst)
(setq auto-mode-alist
      (append '(("\\.txt$" . rst-mode)
                ("\\.rst$" . rst-mode)
                ("\\.rest$" . rst-mode)) auto-mode-alist))

Some helpful functions:

C-c TAB - rst-toc-insert

  Insert table of contents at point

C-c C-u - rst-toc-update

    Update the table of contents at point

C-c C-l rst-shift-region-left

    Shift region to the left

C-c C-r rst-shift-region-right

    Shift region to the right