[issue9625] argparse: Problem with defaults for variable nargs when using choices
James Corbett added the comment:
I would love to get this issue resolved; it seems like everyone agrees that
it's a bug. It came up for me recently: https://bugs.python.org/issue41047.
Judging from the comments above, the consensus is that the relevant line,
`self._check_value(action, value)` should either be replaced with something
like `if isinstance(value, collections.abc.Sequence): for v in value:
self._check_value(action, v)` or be removed entirely.
I think the line should just be removed. I think it's fair to assume that users
of `argparse` know what they're doing, so I think they should be allowed to
pass default values that conflict with `choices`. Also, removing the line makes
the behavior consistent with the optionals, which don't check whether default
values are in `choices`. See the below script:
```
import argparse
def main():
parser = argparse.ArgumentParser()
parser.add_argument("--foo", nargs="+", default=[-1], choices=range(10))
parser.add_argument("--bar", nargs="*", default=-1, choices=range(10))
parser.add_argument("pos", nargs="?", default=-1, choices=range(10))
args = parser.parse_args()
print(args)
if __name__ == '__main__':
main()
```
Which yields:
```
$ python argparse_test.py
Namespace(foo=[-1], bar=-1, pos=-1)
```
--
nosy: +jameshcorbett
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[issue41436] BUG a simple "and" and "or"
James Corbett added the comment:
I think this would have been a better fit for a StackOverflow issue:
https://stackoverflow.com/questions/tagged/python. Also, it's not a compilation
error and it doesn't have anything to do with CPython's testing framework.
Anyway, I don't think this is a bug. For a string `ch`, it is always true that
either `ch != 'n'` or `ch != 'N'`---no string is equal to both `'N'` and `'n'`.
Therefore your `while` condition will always be true and the loop will always
continue.
As you already noted, your loop will terminate properly if you used `and`. You
could also rewrite it as `while ch not in ('n', 'N'):` which I think is clearer.
--
nosy: +jameshcorbett, xtreak
type: compile error -> behavior
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[issue41430] Document C docstring behavior
Change by James Corbett : -- keywords: +patch pull_requests: +20816 stage: -> patch review pull_request: https://github.com/python/cpython/pull/21673 ___ Python tracker <https://bugs.python.org/issue41430> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue41430] Document C docstring behavior
New submission from James Corbett : As described in https://stackoverflow.com/questions/25847035/what-are-signature-and-text-signature-used-for-in-python-3-4, https://bugs.python.org/issue20586, and https://stackoverflow.com/questions/50537407/add-a-signature-with-annotations-to-extension-methods, it is possible to embed a signature in docstrings for C functions, so that `help` and `inspect.signature` work properly on them. However, this functionality isn't documented anywhere. I think something should be added to the "extending and embedding the Python interpreter" tutorial. -- assignee: docs@python components: Documentation messages: 374547 nosy: docs@python, jameshcorbett priority: normal severity: normal status: open title: Document C docstring behavior type: enhancement ___ Python tracker <https://bugs.python.org/issue41430> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue41046] unittest: make skipTest a classmethod
James Corbett added the comment: I was careless in my example, it would need to be `cls.skipTest(reason)`. However, that really doesn't have anything to do with why it should be a `classmethod` instead of an instance method: it's so that you can call `skipTest` from `classmethods`, namely `setUpClass` which is called by the `unittest` framework. You can currently call `skipTest` from `setUpClass` only with something ugly like `cls.skipTest(None, reason)` (i.e. passing `None` for the `self` parameter, which works because `self` isn't used). -- ___ Python tracker <https://bugs.python.org/issue41046> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue41047] argparse: misbehavior when combining positionals and choices
Change by James Corbett : -- keywords: +patch pull_requests: +20172 stage: -> patch review pull_request: https://github.com/python/cpython/pull/20997 ___ Python tracker <https://bugs.python.org/issue41047> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue41047] argparse: misbehavior when combining positionals and choices
New submission from James Corbett :
The `argparse.ArgumentParser` sometimes rejects positional arguments with no
arguments when `choices` is set and `nargs="*"`.
When there are no arguments and `nargs` is `"*"`, the default value is chosen,
or `[]` if there is no default value. This value is then checked against
`choices` and an error message is printed if the value is not in `choices`.
However, sometimes the value is intentionally not in `choices`, and this leads
to problems. An example will explain this much better, and show that the issue
only occurs with the particular combination of positionals, `nargs="*"`, and
`choices`:
```
>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument("foo", choices=["a", "b", "c"], nargs="*")
>>> parser.add_argument("--bar", choices=["d", "e", "f"], nargs="*")
>>> parser.add_argument('--baz', type=int, choices=range(5, 10), default="20")
>>> parser.parse_args("a --bar".split())
Namespace(foo=['a'], bar=[], baz=20)
>>> parser.parse_args(["a"])
Namespace(foo=['a'], bar=None, baz=20)
>>> parser.parse_args([])
usage: [-h] [--bar [{d,e,f} ...]] [--baz {5,6,7,8,9}] [{a,b,c} ...]
: error: argument foo: invalid choice: [] (choose from 'a', 'b', 'c')
```
In this case I could have got around the last error by adding `[]` to choices,
but that pollutes the help and usage messages.
--
components: Library (Lib)
messages: 371915
nosy: jameshcorbett
priority: normal
severity: normal
status: open
title: argparse: misbehavior when combining positionals and choices
type: behavior
versions: Python 3.9
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[issue41046] unittest: make skipTest a classmethod
Change by James Corbett : -- keywords: +patch pull_requests: +20171 stage: -> patch review pull_request: https://github.com/python/cpython/pull/20996 ___ Python tracker <https://bugs.python.org/issue41046> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue41046] unittest: make skipTest a classmethod
New submission from James Corbett : The `unittest.TestCase.skipTest` method, used to skip the current test, is currently an instance method. There's nothing to stop it from being a `classmethod` or a `staticmethod` though---it doesn't use its reference to `self` since it's just a wrapper around the `SkipTest` exception. Making it a `classmethod` or `staticmethod` would allow calling the method from `setUpClass`. Here's an example: ``` import unittest class MyTestCase(unittest.TestCase): @classmethod def ready_for_tests(cls): pass @classmethod def setUpClass(cls): if not cls.ready_for_tests(): cls.skipTest() ``` -- components: Library (Lib) messages: 371914 nosy: jameshcorbett priority: normal severity: normal status: open title: unittest: make skipTest a classmethod type: enhancement versions: Python 3.9 ___ Python tracker <https://bugs.python.org/issue41046> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
