ArgumentParser instance → manual page

Avoid documenting your Python script arguments on two places! This is typically done in an argparse.ArgumentParser help configuration (help=, description=, etc.), and also in a manually crafted manual page.

The good thing about an ArgumentParser objects is that it actually provides a traversable "tree-like" structure, with all the necessary info needed to automatically generate documentation, for example in a groff typesetting system (manual pages). And this is where this project can help.

There are two supported ways to generate the manual, either script it using the installed command argparse-manpage, or via setup.py build automation (with a slight bonus of automatic manual page installation with setup.py install).

What is need?

Most of the (meta)data is stored in the ArgumentParser object, therefore argparse-manpage needs to know its location—it can be either the object itself, or a method to call to get the object [^1].

On top of this, several manual page fields (like author or project name) need to be specified, either on command-line or via setup.py metadata.

Command-line usage

See the following example:

$ argparse-manpage --pyfile ./pythonfile.py --function get_parser \
                   --author "John --author-email doe@example.com" \
                   --project-name myproject --url https://pagure.io/myproject \
> cool-manpage.1

This (a) processes the ./pythonfile.py, (b) calls the get_parser inside to obtain the ArgumentParser instance, (c) transforms it into a manual page and (d) stores it into the cool-manpage.1 file.

Alternatively those options above can be combined with

• option --module mymodule.main, to load a Python module mymodule.main from PYTHONPATH, or
• --object parser_object_name if the parser_object_name is a global variable.

Use with pyproject.toml

First, you need to declare in pyproject.toml that argparse-manpage is needed at build-time and use the setuptools.builds_meta` backend:

[build-system]
requires = ["argparse-manpage[setuptools]"]
build-backend = "setuptools.build_meta"

Alternatively, you can place the build_manpages (sub)directory from this project somewhere onto PYTHONPATH so you can use it at build time. For example:

git submodule add --name build_manpages https://github.com/praiskup/build_manpages
git submodule update --init

Then in pyproject.toml (re)define cmdclass commands:

[tool.setuptools.cmdclass]
build_py = "build_manpages.build_py"
install = "build_manpages.install"
build_manpages = "build_manpages.build_manpages"

And specify the list of built manual pages:

[tool.build_manpages]
manpages = [
    "man/foo.1:object=parser:pyfile=bin/foo.py",
    "man/bar.1:function=get_parser:pyfile=bin/bar",
    "man/baz.1:function=get_parser:pyfile=bin/bar:prog=baz",
]

Use with setup.py

In your setup.py use pattern like:

[...]
from build_manpages import build_manpages, get_build_py_cmd, get_install_cmd

setup(
  [...]
  cmdclass={
      'build_manpages': build_manpages,
      # Re-define build_py and install commands so the manual pages
      # are automatically re-generated and installed
      'build_py': get_build_py_cmd(),
      'install': get_install_cmd(),
  }
)

And in setup.cfg configure the manual pages you want to automatically generate and install:

[build_manpages]
manpages =
    man/foo.1:object=parser:pyfile=bin/foo.py
    man/bar.1:function=get_parser:pyfile=bin/bar
    man/baz.1:function=get_parser:pyfile=bin/bar:prog=baz

List of manual pages

The format of those lines is a colon separated list of arguments/options. The first argument determines the filename of the generated manual page. Then follows a list of options of format option=value. Supported values are:

• pyfile - what python file the argparse object resides in
• object - the name of arparse object in "pyfile" to import
• function - the name of function in pyfile to call to get the argparse object
• format - format of the generated man page: pretty (default), single-commands-section
• author - author of the program; can be specified multiple times
• description - description of the program, used in the NAME section, after the leading 'name - ' part, see man (7) man-pages for more info
• project_name - name of the project the program is part of
• version - version of the project, visible in manual page footer
• prog - value that substitutes %prog in ArgumentParser's usage
• url - link to project download page
• manual_section - section of the manual, by default 1, see man (7) man-pages for more info about existing sections
• manual_title - the title of the manual, by default "Generated Python Manual", see man (7) man-pages for more instructions
• include - a file of extra material to include; see below for the format
• manfile - a file containing a complete man page that just needs to be installed (such files must also be listed in MANIFEST.in)

The values from setup.cfg override values from setup.py's setup(). Note that when manfile is set for a particular page, no other option is allowed.

Then run setup.py build_manpages to build a manpages for your project. Also, if you used get_build_py helper, setup.py build then transitively builds the manual pages.

Include file format

The include file format is based on GNU help2man's --include format.

The format is simple:

[section]
text

/pattern/
text

Blocks of verbatim *roff text are inserted into the output either at the start of the given section (case insensitive), or after a paragraph matching pattern, a Python regular expression.

Lines before the first section are silently ignored and may be used for comments and the like.

Other sections are prepended to the automatically produced output for the standard sections given above, or included near the bottom of the man page, before the AUTHOR section, in the order they occur in the include file.

Placement of the text within the section may be explicitly requested by using the syntax [<section], [=section] or [>section] to place the additional text before, in place of, or after the default output respectively.

Installation

This package is distributed in PyPI, can be installed by:

$ pip install argparse-manpage

It can simply downloaded, or distributed as a git submodule (see above).

Packaging status

The Git snapshot RPMs–pre-release version automatically built from the main branch–are available in Fedora Copr build system

The argparse-manpage project is provided natively on many distributions:

Try your package manager directly (e.g. on Fedora dnf install -y argparse-manpage).

History

The initial code was developed for CrunchyFrog, a database query tool for Gnome. The frog is now retired and RunSQLRun is it's successor. Then, the build_manpage command was developed in andialbrecht and edited slightly in gabrielegiammatteo. There's even an old blog post about this command.

Since some useful work has been done in python pull request, the code from the PR has been used here too.

Later more options and flexibility has been implemented in this fork, with the help of many contributors. Thank you!

Historically, build_manpage setup.py command was provided (mostly for OptionParser). Later we migrated to more versatile build_manpages command. But the old variant is still supported.

License

This work is released under the terms of the Apache License v2.0. See LICENSE for details.

[^1]: argparse-manpage needs to process the location (file/module) via Python interpreter, and thus please avoid side-effects (typically, the main.py files need to use the if __name__ == "__main__" condition, and similar).