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=[email protected]> on behalf of Skip Montanaro <[email protected]>
Date: Sunday, November 27, 2022 at 6:42 PM
To: Python <[email protected]>
Subject: argparse � adding a --version flag in the face of positional args
*** Attention: This is an external email. Use caution responding, opening attachments or clicking on links. ***

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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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=[email protected]> on behalf of Weatherby,Gerard <[email protected]>
Date: Sunday, November 27, 2022 at 10:29 PM
To: Skip Montanaro <[email protected]>, Python <[email protected]> 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=[email protected]> on behalf of Skip Montanaro <[email protected]>
Date: Sunday, November 27, 2022 at 6:42 PM
To: Python <[email protected]>
Subject: argparse � adding a --version flag in the face of positional args
*** Attention: This is an external email. Use caution responding, opening attachments or clicking on links. ***

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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