How can I set up argparse to parse either 'diff -g file1 -r file2' or 'format file'?

Question

I want to use argparse to parse command line arguments for my program. The program supports two modes - diff and format.

When -diff is chosen, the arguments -g <file1> and -r <file2> are also needed. When -format is chosen, instead there should be a <file> argument.

How can I set up this logic with argparse? Should I use subparsers?

Answer 1

Just to share and record what I have finalized eventually. There are two solutions that I tried and eventually I picked up the subparser one although I think both ways work well to suit this task:

1. Using subparser

import argparse

parser = argparse.ArgumentParser()
subparsers = parser.add_subparsers(dest='command')
subparsers.required = True

# subparser for diff
parser_multi = subparsers.add_parser('diff')
# add required arguments
parser_diff.add_argument(
    '-f1',
    '--file1',
    type=str,
    required=True
)
parser_diff.add_argument(
    '-f2',
    '--file2',
    type=str,
    required=True
)

# subparser for format
parser_format = subparsers.add_parser('format')
# add a required argument
parser_format.add_argument(
    '-f',
    '--file',
    type=str,
    required=True
)

args = parser.parse_args()

2. Using conditional args parser

import argparse
import sys

mode_choices = ['diff', 'format']
parser = argparse.ArgumentParser()
parser.add_argument('-m',
                    '--mode',
                    choices=mode_choices,
                    help='Choose mode to start',
                    required=True)

if True in list(map(lambda x: mode_choices[0] in x, sys.argv)):
    parser.add_argument('-f1',
                        '--file1',
                        type=str,
                        required=True)
    parser.add_argument('-f2',
                        '--file2',
                        type=str,
                        required=True)

if True in list(map(lambda x: mode_choices[1] in x, sys.argv)):
    parser.add_argument('-f',
                        '--file',
                        type=str,
                        required=True)

args = parser.parse_args()