Argparse: add method for retrieving the parsers of actions

Feature or enhancement

Proposal:

I have a CLI interface with an argparse.ArgumentParser composed of a bunch of different actions. I was trying to validate if an argument had been set to a default value, and with just the main parser available, I was having some issues using get_default() working from the main parser, rather than the parsers for the various actions.

I ended up going with the following comparison, in order to reduce the amount of refactoring I would need to do, where args is the var holding the object returned from parse_args():

        args.my_param == parser._actions[1].choices[args.action]].get_default(args.my_param)

I could also have solved this by adding a wrapper class holding all the subparsers in an object of some kind.

But - I think it would be nice to have a public method for accessing these action parsers, mostly for enabling this kind of use case.

Has this already been discussed elsewhere?

Not that I could find

Links to previous discussion of this feature:

No response

Start with argparse.ArgumentParser, the parser's _actions collection, subparser choices, and get_default(). Determine the public method's intended scope and behavior for retrieving action parsers, including how it should support the described default-value validation use case. Done means the API and its behavior are clearly defined and the feature is covered by appropriate tests.