argparse Incorrect Handling of Store Actions

[FluxIX]

BPO	28558
Nosy	@zhangyangyu, @FluxIX
Files	test_argparse.py: Example of Error

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2016-10-29.17:29:05.017>
created_at = <Date 2016-10-29.17:21:51.059>
labels = ['type-bug', 'invalid']
title = 'argparse Incorrect Handling of Store Actions'
updated_at = <Date 2016-10-29.17:29:24.421>
user = 'https://github.com/FluxIX'

bugs.python.org fields:

activity = <Date 2016-10-29.17:29:24.421>
actor = 'xiang.zhang'
assignee = 'none'
closed = True
closed_date = <Date 2016-10-29.17:29:05.017>
closer = 'xiang.zhang'
components = []
creation = <Date 2016-10-29.17:21:51.059>
creator = 'Flux'
dependencies = []
files = ['45266']
hgrepos = []
issue_num = 28558
keywords = []
message_count = 2.0
messages = ['279686', '279687']
nosy_count = 2.0
nosy_names = ['xiang.zhang', 'Flux']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue28558'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5']

[FluxIX]

argparse does not handle Store actions correctly when "nargs = 1" is provided. The documentation indicates the value should be assigned to the dest, but instead a list with the value as the only item is assigned to dest.

[zhangyangyu]

This is the expected behaviour. The doc explicitly says "Note that nargs=1 produces a list of one item. This is different from the default, in which the item is produced by itself". Read https://docs.python.org/3/library/argparse.html#nargs.