Hey.

AFAIU, the sole purpose of ArgumentParser.add_argument_group() is for the grouping within the help output.

It would be nice, if one could create a mutually exclusive group (with ArgumentParser.add_mutually_exclusive_group) from/within such a "normal" group, so that the mutually exclusive arguments are listed within the group, but are still, mutually exclusive.

Right now when doing something like:
    parser = argparse.ArgumentParser()
    parser_group = parser.add_argument_group("INPUT OPTIONS")
    parser_group_mutually_exclusive = parser_group.add_mutually_exclusive_group(required=False)
    parser_group_mutually_exclusive.add_argument("--from-args")
    parser_group_mutually_exclusive.add_argument("--from-files")
    parser_group_mutually_exclusive.add_argument("--from-stdin")
    parser_group.add_argument("-0", help="null delimited pathnames")

it works, but the mutually exclusive options are note printed within the "INPUT OPTIONS", but rather at the normal "optional arguments:" section of the help.

The above example also kinda shows what this could be used for:
- one might have e.g. a group for input options, and amongst that the mutually exclusive "--from-*" which specify the source of the input.


Cheers,
Chris.