argparse with required subcommands

There was a change in 3.3 in the error message for required arguments, and subcommands got lost in the dust.

http://bugs.python.org/issue9253#msg186387

There I suggest this work around, setting the required attribute after the subparsers is defined.

parser = ArgumentParser(prog='test')
subparsers = parser.add_subparsers()
subparsers.required = True
subparsers.dest = 'command'
subparser = subparsers.add_parser("foo", help="run foo")
parser.parse_args()

update

A related pull-request: https://github.com/python/cpython/pull/3027

In addition to hpaulj's answer: you can also use the required keyword argument with ArgumentParser.add_subparsers() since Python 3.7. You also need to pass dest as argument. Otherwise you will get an error: TypeError: sequence item 0: expected str instance, NoneType found.

Example file example.py:

import argparse

parser = argparse.ArgumentParser()
subparsers = parser.add_subparsers(dest='command', required=True)
foo_parser = subparsers.add_parser("foo", help="command foo")
args = parser.parse_args()

Output of the call without an argument:

$ python example.py
usage: example.py [-h] {foo} ...
example.py: error: the following arguments are required: command