[New-bugs-announce] [issue24251] Different behavior for argparse between 2.7.8 and 2.7.9 when adding the same arguments to the root and the sub commands

[Hao Huang]

New submission from Hao Huang:

When I was trying to add the same argument to both the root command and the sub command and you put the arguments before the subcommand, In 2.7.8 the arguments would be parsed correctly. But in 2.7.9, they wouldn't but these arguments would show up in the help doc:(

For python2.7.8
~$ python2.7
Python 2.7.8 (default, Oct 29 2014, 13:45:48)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import argparse
>>>
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument("-s", dest="start")
_StoreAction(option_strings=['-s'], dest='start', nargs=None, const=None, default=None, type=None, choices=None, help=None, metavar=None)
>>>
>>> subparsers = parser.add_subparsers()
>>> subparser = subparsers.add_parser("command")
>>> subparser.add_argument("-s", dest="start")
_StoreAction(option_strings=['-s'], dest='start', nargs=None, const=None, default=None, type=None, choices=None, help=None, metavar=None)
>>>
>>> parser.parse_args(["-s", "1", "command"])
Namespace(start='1')
>>> parser.parse_args(["command", "-s", "1"])
Namespace(start='1')

For python 2.7.9
~$ python2.7
Python 2.7.9 (default, Apr 2 2015, 15:33:21)
[GCC 4.9.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument("-s", dest="start")
_StoreAction(option_strings=['-s'], dest='start', nargs=None, const=None, default=None, type=None, choices=None, help=None, metavar=None)
>>>
>>> subparsers = parser.add_subparsers()
>>> subparser = subparsers.add_parser("command")
>>> subparser.add_argument("-s", dest="start")
_StoreAction(option_strings=['-s'], dest='start', nargs=None, const=None, default=None, type=None, choices=None, help=None, metavar=None)
>>>
>>> parser.parse_args(["-s", "1", "command"])
Namespace(start=None)
>>> parser.parse_args(["command", "-s", "1"])
Namespace(start='1')

----------
components: Argument Clinic
messages: 243700
nosy: hhuang, larry
priority: normal
severity: normal
status: open
title: Different behavior for argparse between 2.7.8 and 2.7.9 when adding the same arguments to the root and the sub commands
type: behavior
versions: Python 2.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue24251>
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