rich-argparse 1.1.0

A rich help formatter for argparse

rich-argparse

Format argparse help output using rich.

Installation

Install from PyPI with pip or your favorite tool.

pip install rich-argparse

Or copy the file rich_argparse.py to your project provided you have rich already installed.

Usage

Simply pass formatter_class to the argument parser

import argparse
from rich_argparse import RichHelpFormatter

parser = argparse.ArgumentParser(..., formatter_class=RichHelpFormatter)
...

rich-argparse defines help formatter classes that produce colorful and easy to read help text. The formatter classes are equivalent to argparse's built-in formatters:

rich_argparse formatter	argparse equivalent
RichHelpFormatter	HelpFormatter
RawDescriptionRichHelpFormatter	RawDescriptionHelpFormatter
RawTextRichHelpFormatter	RawTextHelpFormatter
ArgumentDefaultsRichHelpFormatter	ArgumentDefaultsHelpFormatter
MetavarTypeRichHelpFormatter	MetavarTypeHelpFormatter

For more information on how these formatters work, check the argparse documentation.

Output styles

The default styles used by rich-argparse formatters are carefully chosen to work in different light and dark themes. If these styles don't suit your taste, read below to learn how to change them.

Note The examples below only mention RichHelpFormatter but apply to all other formatter classes.

Customize the colors

You can customize the colors in the output by modifying the styles dictionary on the formatter class. By default, RichHelpFormatter defines the following styles:

{
    'argparse.args': 'cyan',  # for positional-arguments and --options (e.g "--help")
    'argparse.groups': 'dark_orange',  # for group names (e.g. "positional arguments")
    'argparse.help': 'default',  # for argument's help text (e.g. "show this help message and exit")
    'argparse.metavar': 'dark_cyan',  # for metavariables (e.g. "FILE" in "--file FILE")
    'argparse.prog': 'grey50',  # for %(prog)s in the usage (e.g. "foo" in "Usage: foo [options]")
    'argparse.syntax': 'bold',  # for highlights of back-tick quoted text (e.g. "`some text`")
    'argparse.text': 'default',  # for the descriptions and epilog (e.g. "A program to foo")
}

For example, to make the description and epilog italic, change the argparse.text style:

RichHelpFormatter.styles["argparse.text"] = "italic"

Customize group name formatting

You can change how the names of the groups (like 'positional arguments' and 'options') are formatted by setting the RichHelpFormatter.group_name_formatter function. By default, RichHelpFormatter sets the function to str.title but any function that takes the group name as an input and returns a str works. For example, to apply the UPPER CASE format do this:

RichHelpFormatter.group_name_formatter = str.upper

Special text highlighting

You can highlight patterns in the help text and the description text of your parser's help output using regular expressions. By default, RichHelpFormatter highlights patterns of --options-with-hyphens using the argparse.args style and patterns of `back tick quoted text` using the argparse.syntax style. You can control what patterns are highlighted by modifying the RichHelpFormatter.highlights list. To disable all highlights, you can clear this list using RichHelpFormatter.highlights.clear().

You can also add custom highlight patterns and styles. The following example highlights all occurrences of pyproject.toml in green.

# Add a style called `pyproject` which applies a green style (any rich style works)
RichHelpFormatter.styles["argparse.pyproject"] = "green"
# Add the highlight regex (the regex group name must match an existing style name)
RichHelpFormatter.highlights.append(r"\b(?P<pyproject>pyproject\.toml)\b")
# Pass the formatter class to argparse
parser = argparse.ArgumentParser(..., formatter_class=RichHelpFormatter)
...

Colors in the usage

RichHelpFormatter colors the usage generated by the formatter using the same styles used to color the arguments and their metavars. If you use a custom usage message in the parser, this text will treated as "plain text" and will not be colored by default. You can enable colors in user defined usage message with console markup by setting RichHelpFormatter.usage_markup = True. If you enable this option, make sure to escape any square brackets in the usage text.

Working with subparsers

If your code uses argparse's subparsers and you want to format the subparsers' help output with rich-argparse, you have to explicitly pass formatter_class to the subparsers since subparsers do not inherit the formatter class from the parent parser by default. You have two options:

1. Create a helper function to set formatter_class automatically:

    subparsers = parser.add_subparsers(...)
   
    def add_parser(*args, **kwds):
        kwds.setdefault("formatter_class", parser.formatter_class)
        return subparsers.add_parser(*args, **kwds)
   
    p1 = add_parser(...)
    p2 = add_parser(...)
   

2. Set formatter_class on each subparser individually:

    subparsers = parser.add_subparsers(...)
    p1 = subparsers.add_parser(..., formatter_class=parser.formatter_class)
    p2 = subparsers.add_parser(..., formatter_class=parser.formatter_class)
   

Working with third party formatters

RichHelpFormatter can be used with third party formatters that do not rely on the private internals of argparse.HelpFormatter. For example, django defines a custom help formatter that is used with its built in commands as well as with extension libraries and user defined commands. To use rich-argparse in your django project, change your manage.py file as follows:

diff --git a/my_project/manage.py b/my_project/manage.py
index 7fb6855..5e5d48a 100755
--- a/my_project/manage.py
+++ b/my_project/manage.py
@@ -1,22 +1,38 @@
 #!/usr/bin/env python
 """Django's command-line utility for administrative tasks."""
 import os
 import sys


 def main():
     """Run administrative tasks."""
     os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'my_project.settings')
     try:
         from django.core.management import execute_from_command_line
     except ImportError as exc:
         raise ImportError(
             "Couldn't import Django. Are you sure it's installed and "
             "available on your PYTHONPATH environment variable? Did you "
             "forget to activate a virtual environment?"
         ) from exc
+
+    from django.core.management.base import BaseCommand, DjangoHelpFormatter
+    from rich_argparse import RichHelpFormatter
+
+    class DjangoRichHelpFormatter(DjangoHelpFormatter, RichHelpFormatter):  # django first
+        """A rich-based help formatter for django commands."""
+
+    original_create_parser = BaseCommand.create_parser
+
+    def create_parser(*args, **kwargs):
+        parser = original_create_parser(*args, **kwargs)
+        parser.formatter_class = DjangoRichHelpFormatter  # set the formatter_class
+        return parser
+
+    BaseCommand.create_parser = create_parser
+
     execute_from_command_line(sys.argv)


 if __name__ == '__main__':
     main()

Now try out some command like: python manage.py runserver --help. Notice how the special ordering of the arguments applied by django is respected by the new help formatter.