Require either of two arguments using argparse

Question

Given:

import argparse

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

print pa.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

Asked By: georg

||

Source

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.

Answered By: jlengrand

Answer 2

If you need some check that is not provided by the module you can always do it manually:

pa = argparse.ArgumentParser()
...
args = pa.parse_args()

if args.foo is None and args.bar is None:
   pa.error("at least one of --foo and --bar required")

Answered By: sth

Require either of two arguments using argparse

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