New submission from Chris Jerdonek:
When passing a string for the choices argument, argparse's usage and error
messages differ from its behavior:
>>> p = argparse.ArgumentParser()
>>> p.add_argument('a', choices='abc')
>>> p.parse_args(['d'])
usage: [-h] {a,b,c}
: error: argument a: invalid choice: 'd' (choose from 'a', 'b', 'c')
>>> p.parse_args(['bc'])
Namespace(a='bc')
This is because argparse uses the "in" operator instead of sequence iteration
to check whether an argument value is valid. Any resolution should also
consider the behavior for string subclasses as well as perhaps bytes-like
objects.
----------
components: Library (Lib)
messages: 180068
nosy: chris.jerdonek
priority: normal
severity: normal
stage: test needed
status: open
title: argparse: mismatch between choices parsing and usage/error message
type: behavior
versions: Python 2.7, Python 3.2, Python 3.3, Python 3.4
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue16977>
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