Believe it or not, the Python project actually provides us a way to do this through various Makefiles. The files utilize the Python Sphinx project to generate a texi file which makeinfo can then convert to info, the format Emacs uses for documentation.
In addition to Python3000, these instructions require GNU Make and Texinfo. These are packaged in most Linux distributions. Different distros may use different naming conventions. Refer to your distro's documentation for the corresponding package names. For Debian based distros:
# install make to utilize the Makefiles provided by the Python project
~/$ sudo apt-get install make
# install texinfo for the `makeinfo` command
~/$ sudo apt-get install texinfo
Package names are usually similar for non-Debian systems. For Windows users, I recommend WSL or creating a virtual machine.
1. Download the documentation
Navigate to https://www.python.org/ftp/python/ and download the tarball for your Python version. It will look like:
https://www.python.org/ftp/python/3.7.9/Python-3.7.9.tar.xz
You can use wget to download the tarball and tar to unpack it. The options x and f are for "extract file":
# download the tarball
~/$ wget https://www.python.org/ftp/python/3.7.9/Python-3.7.9.tar.xz
# extract the tarball
~/$ tar xf Python-3.7.9.tar.xz
2. Run make venv in Python-X.Y.Z/Doc
Sphinx requires more dependencies than are bundled with the basic pip install. Fortunately, the Python project provides a Makefile to create the necessary environment. See the Makefile for precise details.
# Navigate to the Doc/ directory
~/$ cd Python-3.7.9/Doc
# "create a venv with necessary tools"
~/Python-3.7.9/Doc$ make venv
# activate the venv created by make
~/Python-3.7.9/Doc$ source venv/bin/activate
3. Run sphinx-build
Now that the correct environment is set up, we can run Sphinx. This call creates a cache used during generation with the -d option. The documentation files found in the current directory are converted by the texinfo "builder" and output to build/texinfo:
# -b: Use the textinfo builder
# -d: Create "doctree pickles" cache in doctrees/
# Use the current directory as source
# Output to build/texinfo
(venv) ~/Python-3.7.9/Doc$ sphinx-build -b texinfo -d build/doctrees . build/texinfo
4. Use makeinfo to generate the info file
Again, the Python maintainers have given us what we need (even if they haven't documented it well). The previous command created a texi file along with another Makefile. The Makefile calls makeinfo.
# Navigate to the output directory
(venv) ~/Python-3.7.9/Doc$ cd build/texinfo
# Run the generated Makefile
(venv) ~/Python-3.7.9/Doc/build/texinfo$ make
# Hark, unto us an info file is born
(venv) ~/Python-3.7.9/Doc/build/texinfo$ ls
Makefile python-figures python.info python.texi
Like Indiana Jones, you behold the Holy Grail. Many have perished in this journey; you have prevailed. Take a moment to celebrate.
Note: The makeinfo conversion yields errors for me. No matter, I say. The desired info is obtained and I greedily drink from it.
5. Load python.info into Emacs...
Use C-u C-h i to directly open python.info.
To install the info file within the Emacs Help Directory node, first
check C-h v Info-default-directory-list for where info files are stored. Put python.info file there. There may be a file called dir in that directory. The dir file is generated by texinfo and contains the node listing. If no dir file exists, don't worry, that's what we're creating. Note that it's not recommended to edit dir files manually1.
Run update-info-dir in whichever directory you put python.info. This will update (or create) dir with python.info.
For complete details about the texinfo system, see https://www.gnu.org/software/texinfo/manual/texinfo/html_node/Installing-an-Info-File.html.
1Aside from human error, like mistyping a reference, issues may arise due to "malformed" dir files.
