[Python-Dev] PEP 389: argparse - new command line parsing module

Steven Bethard steven.bethard at gmail.com
Wed Sep 30 23:40:20 CEST 2009

On Wed, Sep 30, 2009 at 1:17 PM, Andrew McNabb <amcnabb at mcnabbs.org> wrote:
> >From my cursory reading of the documentation, it looks like argparse can
> only add subparsers for subcommands.  Is there any way to add subparsers
> based on options instead (as iptables does)?

Currently this is not supported, but it would be a nice feature.

> Also, is it possible to add these subparsers dynamically?  For example,
> you would want to be able to load a module immediately after parsing the
> name instead of having to keep a predetermined list of all module names.
> I'm pretty sure that bzr dynamically loads modules this way.  Can
> argparse help with this?

You can probably already do this. I'm not 100% sure what you want to
do, but it's certainly possible to define an argparse.Action that
loads a module when it's invoked. It might look something like::

    class MyAction(argparse.Action):
        def __call__(self, parser, namespace, value, option_string=None):
            mod = __import__(value) # or whatever

Where did you get that preposterous hypothesis?
Did Steve tell you that?
        --- The Hiphopopotamus

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