Introduction

In this post, I will provide you with a comprehensive step-by-step guide on how to create and host documentation for your Python package using Sphinx and Readthedocs. The topics covered in this guide include:

• Setting up Sphinx
• Configuring Sphinx extensions
• Guide to document Python package
• Create documentation modules
• Testing documentation locally
• Setting up Readthedocs
• Automatic deploy documents

Assuming that you already have a Python package in a repository that you want to add documentation to. If not, you can use the fancy_calcy repository as a reference to follow along.

Please keep in mind that the code available in the package is intended solely for demonstration purposes. With that said, let's begin.

---

Setting up Sphinx

Sphinx is a tool that makes it easy to create intelligent and beautiful documentation for Python projects. It is a widely used tool for documenting Python packages. To install Sphinx, run the following command:

pip install sphinx==6.2.1

Note: It's always a good practice to specify the version of the package you are installing. Otherwise you may end up with a broken build in future.

In this guide, we will be using sphinx==6.2.1

Let's create a docs directory in the root of your project. This is where we will store all the documentation files. Use the following command to create the docs directory in the root of your project:

sphinx-quickstart docs

• If you don't specify docs in the above command it will create a source folder instead.
• Once run the above command, it will ask you a series of questions. One of the questions will be to separate the source and build directories. You can choose n to keep it simple. I personally prefer to keep all the documentation in the same directory. However, it's up to you.

Benefits of choosing n: no need to specify the source directory while building the documentation. Only use the following command to build the documentation:

cd docs
make html

Otherwise, you need to specify the source directory while building the documentation:

cd docs
sphinx-build source build

• Once you have answered all the questions, it will create a docs directory with the following structure:

docs/
    _build/
    _static/
    _templates/
    conf.py
    index.rst
    Makefile
    make.bat

• conf.py is the main configuration file for Sphinx. It contains all the settings for the documentation.
• index.rst is the main file where you will write the documentation.
• Makefile and make.bat are the files that contain the commands to build the documentation.
• _build is the directory where the documentation will be built. It will contain the HTML files.
• _static and _templates are the directories that contain the static files and templates for the documentation. It will be used to store the image files, CSS files, and JavaScript files.

We will make changes to the conf.py and index.rst files in the next sections.

---

Configuring Sphinx extensions

Sphinx has a lot of extensions that can be used to enhance the documentation. Some of the popular extensions are mentioned in the requirements_docs.txt file. You can install them using the following command:

cd docs
pip install -r requirements_docs.txt

Most common extensions are: m2r2, myst-parser, sphinx-rtd-theme, sphinxcontrib-napoleon, sphinx-copybutton, sphinx-autodoc-typehints. Pleas keep in mind that the documentation theme is governed by the theme you provide in the conf.py file. In our case we will be using the sphinx-rtd-theme. It's included in the requirements_docs.txt file. The extension name should be provided in conf.py file. We replaced the default theme with sphinx-rtd-theme. Please see the details below:

In conf.py file, add the following lines to enable the extensions:

html_theme = 'sphinx_rtd_theme'

Please make sure the requirements_docs.txt file is present in the docs directory. It will be helpful while deploy the documentation on Readthedocs.

Also add the following lines in conf.py file to enable these extensions:

extensions = [
    'sphinx.ext.autodoc',
    'sphinx.ext.autosummary',
    'sphinx.ext.duration',
    'sphinx.ext.doctest',
    "sphinx.ext.viewcode",
    "sphinx.ext.intersphinx",
    "sphinx.ext.napoleon",
    "sphinx.ext.todo",
    "sphinx.ext.coverage",
    "sphinx.ext.mathjax",
    "sphinx.ext.ifconfig",
    "sphinx_copybutton",
    "sphinx_togglebutton",
    "nbsphinx",
    'numpydoc',
    "IPython.sphinxext.ipython_console_highlighting",
    "IPython.sphinxext.ipython_directive",
    "myst_parser",
    "mdinclude",  # custom module
    "sphinx_rtd_theme",
    "sphinx_autodoc_typehints",
]

We have already included an extension myst_parser and m2r2 which enable us to use markdown in the documentation. However, some of the configuration does not work by default therefore, we need to add the Python file named minclude.py. It's included in the docs directory.

You need to add these lines in the conf.py file to include the mdinclude.py.

import pathlib
import sys
import os

sys.path.insert(0, os.path.abspath("."))
sys.path.insert(0, os.path.abspath("../"))
sys.path.insert(1, os.path.dirname(
    os.path.abspath("../")) + os.sep + "path_to_root_directory")

# in this case path_to_root_directory is fancy_calcy

As of now, we installed the required extensions and configured them in the conf.py file. We will move to the next section to document the Python package.

---

Guide to document Python package

There are different Python docstring style guides which could be used. We will be using the Numpydoc style guide. It's a widely used style guide. You can find the details here. The package used for this is numpydoc. It's included in the requirements_docs.txt file.

The other most popular style guide is Google style guide. You can find the details here and here

You could also see how the function and classed have been documented in the fancy_calcy package. It's included in the fancy_calcy directory. It also includes some mathematical formulas and equations. Also, it provided usage of linking one module inside another module as reference.

---

Create documentation modules

Now, we have completed the basic setup and also Python code is well documented using the Numpydoc style guide. Let's move to the next section to create the module level documentation in the docs directory.

By defualt, the index.rst file contains the following content:

.. fancy-calcy documentation master file, created by
   sphinx-quickstart on Wed Feb 28 23:12:53 2024.
   You can adapt this file completely to your liking, but it should at least
   contain the root `toctree` directive.

Welcome to fancy_calcy's documentation!
=======================================
.. toctree::
   :maxdepth: 2
   :caption: Contents:



Indices and tables
==================

* :ref:`genindex`
* :ref:`modindex`
* :ref:`search`

Consider this as the table of content for the documentation. You can add the modules in the toctree directive. Sphinx looks for this file to build the documentation. It will include the modules mentioned in the toctree directive. If a module is not mentioned in the toctree directive, it will not be included in the documentation.

Let's create some markdown files such as installation.md, about.md, and codeofconduct.md. Now add the following lines in the index.rst file to include these markdown files in the documentation:

.. only new lines are shown here:

.. toctree::
   :name: Getting Started
   :caption: Getting Started
   :maxdepth: 1
   :hidden:

   installation

.. toctree::
   :name: Community
   :caption: Community
   :maxdepth: 1
   :hidden:

   codeofconduct
   about

As of now, we have not done anything to bring the docstrings added to the python files in the documentation. We have on option, we create an api folder inside the docs directory and add all modules and submodules as defined in the Python package.

Like, we have three modules in the fancy_calcy package, namely basics, advanced and triangle. Now, let's folder with the same names in the api directory. Each module inside these folder will contain the index.rst file and .rst files for each function and class.

Let's take an example of the basics module. It contains one Python c;as We will create the following files in the api/basics directory with two files, namely index.rst and BasicOperations.rst.

The docs/api/basics/index.rst file will contain the following content:

.. -*- mode: rst -*-

.. currentmodule:: fancy_calcy.basics

Basic Operations
=================

This module provides some basic functionalities for calculation.

=================================== =========================================================================
 Functions                            Description
=================================== =========================================================================
:class:`BasicOperations`              Provide class methods for addition, substraction etc.
=================================== =========================================================================

.. toctree::
   :maxdepth: 1
   :hidden:

   BasicOperations

This file will used in the main index.rst placed inside docs/ file to include the basics module in the documentation. Similarly, we will create the docs/api/advanced and docs/api/triangle directories with the index.rst and .rst files for each function and class.

Once these modules are created, you can add these modules in the docs/index.rst file to include them in the documentation. You can also add the markdown files in the index.rst file to include them in the documentation.

.. only new lines are shown here:

.. toctree::
   :name: API Docs
   :caption: API Docs
   :maxdepth: 1
   :hidden:

 
   api/basics/index
   api/advanced/index
   api/triangle/index

Now, let's add Python examples to the documentation. We create an examples.rst file in the api directory. It will contain the following content references to the various Python examples included in the advanced_example.rst and simple_example.rst files. The actual Python files are present in the examples directory in the root of the project. Now, include the examples.rst file in the index.rst file to include it in the documentation.

.. only new lines are shown here:

.. toctree::
   :name: Examples
   :caption: Examples
   :maxdepth: 1
   :hidden:

   api/examples

We are all set to build the documentation. We will move to the next section to test the documentation locally.

Testing documentation locally

You can run the following command to build the documentation locally:

cd docs
make clean
make html

Goto the _build directory and open the index.html file in the browser. You will see the documentation with the modules mentioned in the toctree directive.

Check the html rendered documentation, navigate through the different modules and see if the documentation is rendered correctly. If you see any issues, you can fix them and rebuild the documentation using the above command.

Setting up Readthedocs

We would like to host the documentation on Readthedocs. It's a widely used platform to host the documentation. It's free and open source. You can create an account on Readthedocs and import the repository to host the documentation.

Please follow the following steps to create an account on Readthedocs.

Readthedocs uses the readthedocs.yml file to build the documentation. It contains the configuration for the documentation. You can create a .readthedocs.yml file in the root of the project. It will contain the following content:

# .readthedocs.yaml
# Read the Docs configuration file
# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details

# Required
version: 2

# Set the OS, Python version and other tools you might need
build:
  os: ubuntu-22.04
  tools:
    python: "3.10"
    # You can also specify other tool versions:
    # nodejs: "19"
    # rust: "1.64"
    # golang: "1.19"

# Build documentation in the "docs/" directory with Sphinx
sphinx:
  configuration: docs/conf.py

# Optionally build your docs in additional formats such as PDF and ePub
formats:
   - pdf
#    - epub

# Optional but recommended, declare the Python requirements required
# to build your documentation
# See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
python:
   install:
   - requirements: docs/requirements_docs.txt

1. Create a Readthedocs account using your GitHub account.
2. Click on the Import a Project button.
3. Select the repository you would like to import.
4. Select the branch you would like to build the documentation from, generally it's main.
5. Finally Build the documentation.

We followed the same approach, now the documentation is hosted on Readthedocs. You can access the documentation using the following link: fancy_calcy.

Automatic deploy documents

Now, you have hosted the documentation on Readthedocs. Nevertheless, the documents get updated time to time. It's a good practice to automate the deployment of the documentation. You can use the following steps to automate the deployment of the documentation:

You have selected the main branch to build the documentation. Therefore, any changes made to the main branch will trigger the build of the documentation. You can also select the tags to build the documentation. It's up to you.

You are all set to build the documentation for your own Python package. You can use the same approach to document any Python package. You can also use the fancy_calcy package as a reference to document your own package.

Conclusion

In this guide, we have covered the steps to create and host documentation for your Python package using Sphinx and Readthedocs. We have also discussed the importance of documentation and the benefits it provides to developers and users.

I hope you find this guide helpful. If you have any questions or suggestions, please feel free to reach out to me. I would be happy to help you. Thank you for reading!