Add section on Python code preparation

Author: astrojuanlu

doc/tutorial/describing-code.rst

@@ -111,3 +111,74 @@ And finally, this is how the result would look like:
    HTML result of documenting a Python function in Sphinx with cross-references
 
 Beautiful, isn't it?
+
+Including doctests in your documentation
+----------------------------------------
+
+Since you are now describing code from a Python library, it will become useful
+to keep both the documentation and the code as synchronized as possible.
+One of the ways to do that in Sphinx is to include code snippets in the
+documentation, called *doctests*, that are executed when the documentation is
+built.
+
+To demonstrate doctests and other Sphinx features covered in this tutorial,
+you will need to setup some basic Python infrastructure first.
+
+Preparing the Python library
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Begin by activating the virtual environment (as seen in the :ref:`getting
+started <tutorial-getting-started>` section of the tutorial) and install
+`flit <https://pypi.org/project/flit/>`_ on it:
+
+.. code-block:: console
+
+   $ source .venv/bin/activate
+   (.venv) $ python -m pip install "flit~=3.3"
+
+Next, create two files on the same level as ``README.rst``: ``pyproject.toml``
+and ``lumache.py``, with these contents:
+
+.. code-block:: toml
+   :caption: pyproject.toml
+
+   [build-system]
+   requires = ["flit_core >=3.2,<4"]
+   build-backend = "flit_core.buildapi"
+
+   [project]
+   name = "lumache"
+   authors = [{name = "Graziella", email = "graziella@lumache"}]
+   dynamic = ["version", "description"]
+
+.. code-block:: python
+   :caption: lumache.py
+
+   """
+   Lumache - Python library for cooks and food lovers.
+   """
+
+   __version__ = "0.1.0"
+
+And finally, install your own code and check that importing it works:
+
+.. code-block:: console
+
+   (.venv) $ flit install --symlink
+   ...
+   (.venv) $ python -c 'import lumache; print("OK!")'
+   OK!
+
+Congratulations! You have created a basic Python library.
+
+.. note::
+
+   The ``pyproject.toml`` file you created above is required so that
+   your library can be installed. On the other hand,
+   ``flit install --symlink`` is an alternative to ``pip install .``
+   that removes the need to reinstall the library every time you make
+   a change, which is convenient.
+
+   An alternative is to not create ``pyproject.toml`` at all,
+   and setting the :envvar:`PYTHONPATH`, :py:data:`sys.path`, or
+   equivalent. However, the ``pyproject.toml`` approach is more robust.

doc/tutorial/getting-started.rst

@@ -1,6 +1,8 @@
 Getting started
 ===============
 
+.. _tutorial-getting-started:
+
 Setting up your project and development environment
 ---------------------------------------------------