New submission from Joannah Nanjekye <nanjekyejoan...@gmail.com>:
Currently, when `parser.add_argument()` is given argument with
`action='store_const'` and no `const` argument , it throws an exception :
>>> from argparse import ArgumentParser
>>> parser = ArgumentParser()
>>> parser.add_argument("--foo", help="foo", action='store_const')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/captain/projects/cpython/Lib/argparse.py", line 1350, in
add_argument
action = action_class(**kwargs)
TypeError: __init__() missing 1 required positional argument: 'const'
>>>
Specifying the `const` argument stops this exception:
>>> parser.add_argument("--foo", help="foo", action='store_const', const=None)
_StoreConstAction(option_strings=['--foo'], dest='foo', nargs=0, const=None,
default=None, type=None, choices=None, help='foo', metavar=None)
Originally the docs, said when `action` was set to` 'store_const'` `const`
defaulted to `None` which was not matching with the implementation at the time.
After this commit :
https://github.com/python/cpython/commi/b4912b8ed367e540ee060fe912f841cc764fd293,
The docs were updated to match the implementation to fix Bpo issues :
https://bugs.python.org/issue25299
https://bugs.python.org/issue24754 and
https://bugs.python.org/issue25314
I suggest that we make `const` default to `None` If `action='store_const'` as
was intended originally before edits to the docs. If no one objects, I can open
a PR for this.
----------
messages: 349911
nosy: A. Skrobov, nanjekyejoannah, r.david.murray
priority: normal
severity: normal
status: open
title: For argparse add_argument with action='store_const', const should
default to None.
versions: Python 3.9
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue37880>
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