argparse: some mutually exclusive arguments in required group

Question

I have a set of arguments that can logically be separated in 2 groups:

• Actions: A1, A2, A3, etc.
• Informations:

Answer 1

There's nothing hacky about verifying arguments after they've been parsed. Just collect them all in a single set, then confirm that it is not empty and contains at most one action.

actions = {"a1", "a2", "a3"}
informations = {"i1", "i2", "i3"}
p = argparse.ArgumentParser()
# Contents of actions and informations contrived
# to make the example short. You may need a series
# of calls to add_argument to define the options and
# constants properly
for ai in actions + informations:
    p.add_argument("--" + ai, action='append_const', const=ai, dest=infoactions)

args = p.parse_args()
if not args.infoactions:
    p.error("At least one action or information required")
elif len(actions.intersection(args.infoactions)) > 1:
    p.error("At most one action allowed")