argparse optional subparser (for --version)

Question

I have the following code (using Python 2.7):

# shared command line options, like --version or --verbose
parser_shared = argparse.ArgumentParser(add_help=Fal         


        

Answer 1

As discussed in http://bugs.python.org/issue9253 (argparse: optional subparsers), as of Python 3.3, subparsers are now optional. This was an unintended result of a change in how parse_args checked for required arguments.

I found a fudge that restores the previous (required subparsers) behavior, explicitly setting the required attribute of the subparsers action.

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

See that issue for more details. I expect that if and when this issue gets properly patched, subparsers will be required by default, with some sort of option to set its required attribute to False. But there is a big backlog of argparse patches.