Specify and check for mutually exclusive arguments in argparse

argparse_conflicts.py

from argparse import ArgumentParser, Action
from enum import Enum, auto


class ArgumentsEnum(Enum):
    opt1 = auto()
    opt2 = auto()

    def __str__(self):
        return "'{}'".format(self.name)


def RecordUserSetAction_(arg_enum):
    class RecordUserSetAction(Action):
        def __call__(self, parser, namespace, values, option_string=None):
            parser.args_user_set.add(arg_enum)
            setattr(namespace, self.dest, values)
    return RecordUserSetAction


class ArgumentParserWithConflicts(ArgumentParser):
    def __init__(self, *args, **kwargs):
        self.conflicts = []
        self.args_user_set = set()

        super(ArgumentParserWithConflicts, self).__init__(*args, **kwargs)

    def set_conflict(self, *args):
        self.conflicts.append(set(args))

    def check_conflicts(self):
        for conflict in self.conflicts:
            if conflict.issubset(self.args_user_set):
                raise ValueError(
                    'These arguments are mutually exclusive: [{}]'
                    ''.format(', '.join(sorted(map(str, conflict))))
                )

    def parse_args(self, args=None, namespace=None):
        args_ = super(ArgumentParserWithConflicts, self).parse_args(
            args=args, namespace=namespace
        )
        self.check_conflicts()
        return args_


def build_parser():
    parser = ArgumentParserWithConflicts()

    parser.add_argument(
        '--optional1', type=str, default='blah', nargs=1,
        action=RecordUserSetAction_(ArgumentsEnum.opt1)
    )

    parser.add_argument(
        '--optional2', default=(3, 3), nargs=2,
        action=RecordUserSetAction_(ArgumentsEnum.opt2)
    )

    # All arguments here should be mutually exclusive.
    parser.set_conflict(ArgumentsEnum.opt1, ArgumentsEnum.opt2)

    return parser


def main():
    parser = build_parser()
    args = parser.parse_args()

    print('Survived, args: {}'.format(args))
    print('None-defaults: {}'.format(parser.args_user_set))


if __name__ == '__main__':
    main()