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

16

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()

answered Feb 28, 2018 at 21:21

adrtam

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3 Comments

Filip S. Over a year ago

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.

adrtam Over a year ago

@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.

CVAUGHN Over a year ago

You can add a required=True to subparsers = parser.add_subparsers() to have argparse run the check for you.

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