Automatic documentation generation from code

In the previous section of the tutorial you manually documented a Python function in Sphinx. However, the description was out of sync with the code itself, since the function signature was not the same. Besides, it would be nice to reuse Python docstrings in the documentation, rather than having to write the information in two places.

Fortunately, the autodoc extension provides this functionality.

Reusing signatures and docstrings with autodoc

To use autodoc, first add it to the list of enabled extensions:

docs/source/conf.py
extensions = [
    'sphinx.ext.duration',
    'sphinx.ext.doctest',
    'sphinx.ext.autodoc',
]

Next, move the content of the .. py:function directive to the function docstring in the original Python file, as follows:

lumache.py
def get_random_ingredients(kind=None):
    """
    Return a list of random ingredients as strings.

    :param kind: Optional "kind" of ingredients.
    :type kind: list[str] or None
    :raise lumache.InvalidKindError: If the kind is invalid.
    :return: The ingredients list.
    :rtype: list[str]

    """
    return ["shells", "gorgonzola", "parsley"]

Finally, replace the .. py:function directive from the Sphinx documentation with autofunction:

docs/source/usage.rst
you can use the ``lumache.get_random_ingredients()`` function:

.. autofunction:: lumache.get_random_ingredients

If you now build the HTML documentation, the output will be the same! With the advantage that it is generated from the code itself. Sphinx took the reStructuredText from the docstring and included it, also generating proper cross-references.

You can also autogenerate documentation from other objects. For example, add the code for the InvalidKindError exception:

lumache.py
class InvalidKindError(Exception):
    """Raised if the kind is invalid."""
    pass

And replace the .. py:exception directive with autoexception as follows:

docs/source/usage.rst
or ``"veggies"``. Otherwise, :py:func:`lumache.get_random_ingredients`
will raise an exception.

.. autoexception:: lumache.InvalidKindError

And again, after running make html, the output will be the same as before.

Generating comprehensive API references

While using sphinx.ext.autodoc makes keeping the code and the documentation in sync much easier, it still requires you to write an auto* directive for every object you want to document. Sphinx provides yet another level of automation: the autosummary extension.

The autosummary directive generates documents that contain all the necessary autodoc directives. To use it, first enable the autosummary extension:

docs/source/conf.py
extensions = [
   'sphinx.ext.duration',
   'sphinx.ext.doctest',
   'sphinx.ext.autodoc',
   'sphinx.ext.autosummary',
]

Next, create a new api.rst file with these contents:

docs/source/api.rst
API
===

.. autosummary::
   :toctree: generated

   lumache

Remember to include the new document in the root toctree:

docs/source/index.rst
Contents
--------

.. toctree::

   usage
   api

Finally, after you build the HTML documentation running make html, it will contain two new pages:

  • api.html, corresponding to docs/source/api.rst and containing a table with the objects you included in the autosummary directive (in this case, only one).

  • generated/lumache.html, corresponding to a newly created reStructuredText file generated/lumache.rst and containing a summary of members of the module, in this case one function and one exception.

Summary page created by autosummary

Summary page created by autosummary

Each of the links in the summary page will take you to the places where you originally used the corresponding autodoc directive, in this case in the usage.rst document.

Note

The generated files are based on Jinja2 templates that can be customized, but that is out of scope for this tutorial.