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+Automatic documentation generation from code
+============================================
+
+In the :ref:`previous section <tutorial-describing-objects>` 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 :pep:`Python docstrings
+<257#what-is-a-docstring>` in the documentation, rather than having to write
+the information in two places.
+
+Fortunately, :doc:`the autodoc extension </usage/extensions/autodoc>` provides this
+functionality.
+
+Reusing signatures and docstrings with autodoc
+----------------------------------------------
+
+To use autodoc, first add it to the list of enabled extensions:
+
+.. code-block:: python
+   :caption: docs/source/conf.py
+   :emphasize-lines: 4
+
+   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:
+
+.. code-block:: python
+   :caption: lumache.py
+   :emphasize-lines: 2-11
+
+   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 :rst:dir:`autofunction`:
+
+.. code-block:: rst
+   :caption: docs/source/usage.rst
+   :emphasize-lines: 3
+
+   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:
+
+.. code-block:: python
+   :caption: lumache.py
+
+   class InvalidKindError(Exception):
+       """Raised if the kind is invalid."""
+       pass
+
+And replace the ``.. py:exception`` directive with :rst:dir:`autoexception`
+as follows:
+
+.. code-block:: rst
+   :caption: docs/source/usage.rst
+   :emphasize-lines: 4
+
+   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 :doc:`autosummary </usage/extensions/autosummary>` extension.
+
+The :rst:dir:`autosummary` directive generates documents that contain all the
+necessary ``autodoc`` directives. To use it, first enable the autosummary
+extension:
+
+.. code-block:: python
+   :caption: docs/source/conf.py
+   :emphasize-lines: 5
+
+   extensions = [
+      'sphinx.ext.duration',
+      'sphinx.ext.doctest',
+      'sphinx.ext.autodoc',
+      'sphinx.ext.autosummary',
+   ]
+
+Next, create a new ``api.rst`` file with these contents:
+
+.. code-block:: rst
+   :caption: docs/source/api.rst
+
+   API
+   ===
+
+   .. autosummary::
+      :toctree: generated
+
+      lumache
+
+Remember to include the new document in the root toctree:
+
+.. code-block:: rst
+   :caption: docs/source/index.rst
+   :emphasize-lines: 7
+
+   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 reST file
+  ``generated/lumache.rst`` and containing a summary of members of the module,
+  in this case one function and one exception.
+
+.. figure:: /_static/tutorial/lumache-autosummary.png
+   :width: 80%
+   :align: center
+   :alt: 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 <https://jinja2docs.readthedocs.io/>`_ that
+   :ref:`can be customized <autosummary-customizing-templates>`,
+   but that is out of scope for this tutorial.