Require either of two arguments using argparse

Question

Given:

import argparse

parser = argparse.ArgumentParser()
parser.add_argument('--foo')
parser.add_argument('--bar')

print(parser.parse_args('--foo 1'.split()))

How do I

• make at least one of "foo, bar" mandatory: --foo x, --bar y and --foo x --bar y are fine
• make at most one of "foo, bar" mandatory: --foo x or --bar y are fine, --foo x --bar y is not

Answer 1

I think you are searching for something like mutual exclusion (at least for the second part of your question).

This way, only --foo or --bar will be accepted, not both.

import argparse

parser = argparse.ArgumentParser()
group = parser.add_mutually_exclusive_group(required=True)
group.add_argument('--foo',action=.....)
group.add_argument('--bar',action=.....)
args = parser.parse_args()

BTW, just found another question referring to the same kind of issue.