Re: argparse — adding a --version flag in the face of positional args

[Weatherby,Gerard]

More better:


import argparse

parser = argparse.ArgumentParser()
parser.add_argument("positional",type=int)
parser.add_argument('--version',action="version",version="2.0")
args = parser.parse_args()
# double argument
print(args.positional * 2)


From: Python-list <python-list-bounces+gweatherby=uchc.edu at python.org> on behalf of Weatherby,Gerard <gweatherby at uchc.edu>
Date: Sunday, November 27, 2022 at 10:29 PM
To: Skip Montanaro <skip.montanaro at gmail.com>, Python <python-list at python.org>
Subject: Re: argparse — adding a --version flag in the face of positional args
Use two parsers:

import argparse
import sys

vparser = argparse.ArgumentParser(add_help=False)
vparser.add_argument('--version',action="store_true",help="show version")
# look for version, ignore remaining arguments
vargs, _ = vparser.parse_known_args()
if vargs.version:
    print("Version 2.0")
    sys.exit(0)
parser = argparse.ArgumentParser()
parser.add_argument("positional",type=int)
# add version again, so it displays if --help called
parser.add_argument('--version',action="store_true",help="show version")
args = parser.parse_args()
# double argument
print(args.positional * 2)


From: Python-list <python-list-bounces+gweatherby=uchc.edu at python.org> on behalf of Skip Montanaro <skip.montanaro at gmail.com>
Date: Sunday, November 27, 2022 at 6:42 PM
To: Python <python-list at python.org>
Subject: argparse — adding a --version flag in the face of positional args
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I have a script to which I'd like to add a --version flag. It should print
the version number then exit, much in the same way --help prints the help
text then exits. I haven't been able to figure that out. I always get a
complaint about the required positional argument.

I think I could use something like nargs='*', but that would push off
detection of the presence of the positional arg to the application.
Shouldn't I be able to tell argparse I'm going to process --verbose, then
exit?

Thx,

Skip
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