Python Language Conceptual grouping of arguments with argparse.add_argument_group()


Example

When you create an argparse ArgumentParser() and run your program with '-h' you get an automated usage message explaining what arguments you can run your software with. By default, positional arguments and conditional arguments are separated into two categories, for example, here is a small script (example.py) and the output when you run python example.py -h.

import argparse

parser = argparse.ArgumentParser(description='Simple example')
parser.add_argument('name', help='Who to greet', default='World')
parser.add_argument('--bar_this')
parser.add_argument('--bar_that')
parser.add_argument('--foo_this')
parser.add_argument('--foo_that')
args = parser.parse_args()
usage: example.py [-h] [--bar_this BAR_THIS] [--bar_that BAR_THAT]
                        [--foo_this FOO_THIS] [--foo_that FOO_THAT]
                        name

Simple example

positional arguments:
  name                 Who to greet

optional arguments:
  -h, --help           show this help message and exit
  --bar_this BAR_THIS
  --bar_that BAR_THAT
  --foo_this FOO_THIS
  --foo_that FOO_THAT

There are some situations where you want to separate your arguments into further conceptual sections to assist your user. For example, you may wish to have all the input options in one group, and all the output formating options in another. The above example can be adjusted to separate the --foo_* args from the --bar_* args like so.

import argparse

parser = argparse.ArgumentParser(description='Simple example')
parser.add_argument('name', help='Who to greet', default='World')
# Create two argument groups
foo_group = parser.add_argument_group(title='Foo options')
bar_group = parser.add_argument_group(title='Bar options')
# Add arguments to those groups
foo_group.add_argument('--bar_this')
foo_group.add_argument('--bar_that')
bar_group.add_argument('--foo_this')
bar_group.add_argument('--foo_that')
args = parser.parse_args()

Which produces this output when python example.py -h is run:

usage: example.py [-h] [--bar_this BAR_THIS] [--bar_that BAR_THAT]
                        [--foo_this FOO_THIS] [--foo_that FOO_THAT]
                        name

Simple example

positional arguments:
  name                 Who to greet

optional arguments:
  -h, --help           show this help message and exit

Foo options:
  --bar_this BAR_THIS
  --bar_that BAR_THAT

Bar options:
  --foo_this FOO_THIS
  --foo_that FOO_THAT