[New-bugs-announce] [issue24441] In argparse add_argument() allows the empty choices argument

[py.user]

New submission from py.user:

A script, configuring argparse to have no choices:

#!/usr/bin/env python3

import argparse

parser = argparse.ArgumentParser()
parser.add_argument('foo', choices=[])

args = parser.parse_args()
print(args)


Running it:

[guest at localhost args]$ ./t.py
usage: t.py [-h] {}
t.py: error: too few arguments
[guest at localhost args]$ ./t.py a
usage: t.py [-h] {}
t.py: error: argument foo: invalid choice: 'a' (choose from )
[guest at localhost args]$ ./t.py ""
usage: t.py [-h] {}
t.py: error: argument foo: invalid choice: '' (choose from )
[guest at localhost args]$

[guest at localhost args]$ ./t.py -h
usage: t.py [-h] {}

positional arguments:
  {}

optional arguments:
  -h, --help  show this help message and exit
[guest at localhost args]$


ISTM, it should throw an exception about empty choices rather than show help with empty choices.

----------
components: Library (Lib)
messages: 245277
nosy: py.user
priority: normal
severity: normal
status: open
title: In argparse add_argument() allows the empty choices argument
type: behavior
versions: Python 3.3, Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue24441>
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