Choices are shown for each flags in argParser python

Question

argParser.add_argument(
            "--operation",
            "-o",
            action="store",
            required=True,
            choices=["VIEW","ADD","EDIT","DELETE"],
            type=str.upper
        )

Actual Output:

root$ myArg -h
required arguments:
  --operation {VIEW,ADD,EDIT,DELETE,INFO}, -o {VIEW,ADD,EDIT,DELETE,INFO}

Required Output:

root$ myArg -h
required arguments:
  --operation/-o {VIEW,ADD,EDIT,DELETE,INFO}

Thanks in advance

Does this answer your question? [Don't show long options twice in print\_help() from argparse](https://stackoverflow.com/questions/18275023/dont-show-long-options-twice-in-print-help-from-argparse) — wjandrea, Apr 14 '20 at 15:43
Simplest fix is use a `metavar`, and list the choices in the help. Combining flags requires more advanced code modification. — hpaulj, Apr 14 '20 at 15:47

mojo · Answer 1 · 2020-04-14T16:16:18.043

The short answer to your question is: your requirements are contrary to what the module does.

Consider argparse.py:652 (version 1.1; Anaconda3, python 3.7.6)

    # if the Optional takes a value, format is:
    #    -s ARGS, --long ARGS
    else:
        default = self._get_default_metavar_for_optional(action)
        args_string = self._format_args(action, default)
        for option_string in action.option_strings:
            parts.append('%s %s' % (option_string, args_string))

What you see is the explicitly intended behavior.

I don't see any obvious parameters that would alter this behavior. The only option I see (after, admittedly, 3 minutes of looking) is to create a custom formatter that is exactly like the default one with the offending method (_format_action_invocation) overridden so that you can do something different than the shipped behavior.

Here's an example of something that at least has the trait of doing what you want. I copied the code from argparse.py and changed the offending code to do what you'd prefer.

import argparse

class CustomFormatter(argparse.HelpFormatter):
    def _format_action_invocation(self, action):
        if action.option_strings and action.nargs != 0:
            # This is the code path that we don't like.
            default = self._get_default_metavar_for_optional(action)
            args_string = self._format_args(action, default)
            return '%s %s' % ('/'.join(action.option_strings), args_string)

        # For everything else, use the default behavior.
        return super()._format_action_invocation(action)

argParser = argparse.ArgumentParser( formatter_class = CustomFormatter )
argParser.add_argument(
            "--operation",
            "-o",
            action="store",
            required=True,
            choices=["VIEW","ADD","EDIT","DELETE"],
            type=str.upper
        )

argParser.parse_args()

Here's the output:

# python soln.py --help
usage: soln.py [-h] --operation {VIEW,ADD,EDIT,DELETE}

optional arguments:
  -h, --help            show this help message and exit
  --operation/-o {VIEW,ADD,EDIT,DELETE}

This, of course, has the disadvantage of being very sensitive to updates to argparse.py. — mojo, Apr 14 '20 at 16:17
But, it looks like this function [hasn't changed in the past 9 years](https://github.com/python/cpython/blame/master/Lib/argparse.py#L547). — mojo, Apr 14 '20 at 16:28

Choices are shown for each flags in argParser python

1 Answers1