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name Punditsdkoslkdosdkoskdo

Get selected subcommand with argparse

When I use subcommands with python argparse, I can get the selected arguments.

parser = argparse.ArgumentParser()
parser.add_argument('-g', '--global')
subparsers = parser.add_subparsers()   
foo_parser = subparsers.add_parser('foo')
foo_parser.add_argument('-c', '--count')
bar_parser = subparsers.add_parser('bar')
args = parser.parse_args(['-g, 'xyz', 'foo', '--count', '42'])
# args => Namespace(global='xyz', count='42')

So args doesn't contain 'foo'. Simply writing sys.argv[1] doesn't work because of the possible global args. How can I get the subcommand itself?

The very bottom of the Python docs on argparse sub-commands explains how to do this:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('-g', '--global')
>>> subparsers = parser.add_subparsers(dest="subparser_name") # this line changed
>>> foo_parser = subparsers.add_parser('foo')
>>> foo_parser.add_argument('-c', '--count')
>>> bar_parser = subparsers.add_parser('bar')
>>> args = parser.parse_args(['-g', 'xyz', 'foo', '--count', '42'])
>>> args
Namespace(count='42', global='xyz', subparser_name='foo')

You can also use the set_defaults() method referenced just above the example I found.

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ArgumentParser.add_subparsers has dest formal argument described as:

dest - name of the attribute under which sub-command name will be stored; by default None and no value is stored

In the example below of a simple task function layout using subparsers, the selected subparser is in parser.parse_args().subparser.

import argparse

def task_a(alpha):
    print('task a', alpha)

def task_b(beta, gamma):
    print('task b', beta, gamma)

if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    subparsers = parser.add_subparsers(dest='subparser')

    parser_a = subparsers.add_parser('task_a')
        '-a', '--alpha', dest='alpha', help='Alpha description')

    parser_b = subparsers.add_parser('task_b')
        '-b', '--beta', dest='beta', help='Beta description')
        '-g', '--gamma', dest='gamma', default=42, help='Gamma description')

    kwargs = vars(parser.parse_args())
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