argparse subparsers with functions

Question

Hello I am starting with argparse. My goal is to build a CLI with main commands that accept arguments and redirect to the corresponding commands functions. Here is what I did so far:

def main(): parser = argparse.ArgumentParser() subparsers = parser.add_subparsers() command1_parser = subparsers.add_parser('command1') command1_parser.set_defaults(func=command1) command1_parser.add_argument('--name', dest='name') command2_parser = subparsers.add_parser('command2') command2_parser.set_defaults(func=command2) command2_parser.add_argument('--frequency', dest='frequency') args = parser.parse_args() def command1(): # do something with args.name def command2(): # do something with args.frequency if __name__ == '__main__': main()

When I do:

entrypoint command1 --name Hello

Or:

entrypoint command2 --frequency 10

It fails to catch the corresponding args. What I am doing wrong? Thanks!

Look at the full subparsers set_defaults example in the docs. — hpaulj
– hpaulj, Commented Feb 28, 2018 at 21:32

adrtam · Accepted Answer · 2018-02-28 21:21:05Z

Because you need to invoke the function manually by args.func(args):

import argparse def main(): parser = argparse.ArgumentParser() subparsers = parser.add_subparsers() command1_parser = subparsers.add_parser('command1') command1_parser.set_defaults(func=command1) command1_parser.add_argument('--name', dest='name') command2_parser = subparsers.add_parser('command2') command2_parser.set_defaults(func=command2) command2_parser.add_argument('--frequency', dest='frequency') args = parser.parse_args() args.func(args) def command1(args): print("command1: %s" % args.name) def command2(args): print("comamnd2: %s" % args.frequency) if __name__ == '__main__': main()

This throws the error AttributeError: 'Namespace' object has no attribute 'func' at the line args.func(args) if the program is run without any arguments.
@FilipS. right. This is just the minimal change to make the OP's code to work. Whoever use this code should add relevant sanitation checks.
You can add a required=True to subparsers = parser.add_subparsers() to have argparse run the check for you.

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