argparse: parse_args with a subparser + namespace tries to setdefault on a mappingproxy object #116850

alex-tianhuang · 2024-03-15T05:26:11Z

Bug report

Bug description:

I was using the namespace argument in parse_args and found that argparse tries to setdefault on a mapping proxy when parsing unknown extra attributes:

import argparse


parser = argparse.ArgumentParser()
subparser = argparse.ArgumentParser()
subparsers = parser.add_subparsers()
subparsers.add_parser(name="sub", add_help=False)


class MyNamespace:
    pass


try:
    parser.parse_args(["sub", "oops"], namespace=MyNamespace)
except SystemExit:
    pass

Traceback (most recent call last):
File "<path_to_script>", line 16, in <module>
parser.parse_args(["sub", "oops"], namespace=MyNamespace)
File "<python_installation>/lib/python3.12/argparse.py", line 1891, in parse_args
args, argv = self.parse_known_args(args, namespace)
File "<python_installation>/lib/python3.12/argparse.py", line 1924, in parse_known_args
namespace, args = self._parse_known_args(args, namespace)
File "<python_installation>/lib/python3.12/argparse.py", line 2139, in _parse_known_args
stop_index = consume_positionals(start_index)
File "<python_installation>/lib/python3.12/argparse.py", line 2095, in consume_positionals
take_action(action, args)
File "<python_installation>/lib/python3.12/argparse.py", line 2000, in take_action
action(self, namespace, argument_values, option_string)
File "<python_installation>/lib/python3.12/argparse.py", line 1268, in call
vars(namespace).setdefault(_UNRECOGNIZED_ARGS_ATTR, [])
AttributeError: 'mappingproxy' object has no attribute 'setdefault'

I suspect this is because we're attempting to do vars(MyNamespace) instead of vars(argparse.Namespace) but I don't know much more than that.

I skimmed the top couple entries on the issue tracker with keywords 'argparse mappingproxy / argparse namespace' and found nothing, so I've decided that maybe nobody has reported this yet.

Using python 3.12.1 / argparse 1.1 / osx-arm64.

CPython versions tested on:

3.12

Operating systems tested on:

macOS

Linked PRs

The text was updated successfully, but these errors were encountered:

mimros · 2024-05-14T18:50:09Z

Hi, I had same issue. I think you have to create instance of your namespace class.

class MyNamespace:
    pass


try:
    my_namespace = MyNamespace() <---------------------------------------------
    parser.parse_args(["sub", "oops"], namespace=my_namespace)
except SystemExit:
    pass

https://docs.python.org/3/library/argparse.html#argparse.Namespace

…le dict It now always uses setattr() instead of setting the dict item to modify the namespace. This allows to use a class as a namespace.

GH-124667) It now always uses setattr() instead of setting the dict item to modify the namespace. This allows to use a class as a namespace.

…le dict (pythonGH-124667) It now always uses setattr() instead of setting the dict item to modify the namespace. This allows to use a class as a namespace. (cherry picked from commit 95e92ef) Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

…ble dict (GH-124667) (GH-124758) It now always uses setattr() instead of setting the dict item to modify the namespace. This allows to use a class as a namespace. (cherry picked from commit 95e92ef) Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

…ble dict (GH-124667) (GH-124757) It now always uses setattr() instead of setting the dict item to modify the namespace. This allows to use a class as a namespace. (cherry picked from commit 95e92ef) Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

alex-tianhuang added the type-bug An unexpected behavior, bug, or error label Mar 15, 2024

sobolevn added this to Argparse issues Mar 15, 2024

bedevere-app bot mentioned this issue Sep 27, 2024

gh-116850: Fix argparse for namespaces with not directly writable dict #124667

Merged

serhiy-storchaka self-assigned this Sep 28, 2024

serhiy-storchaka added a commit that referenced this issue Sep 29, 2024

gh-116850: Fix argparse for namespaces with not directly writable dict (

95e92ef

GH-124667) It now always uses setattr() instead of setting the dict item to modify the namespace. This allows to use a class as a namespace.

This was referenced Sep 29, 2024

[3.13] gh-116850: Fix argparse for namespaces with not directly writable dict (GH-124667) #124757

Merged

[3.12] gh-116850: Fix argparse for namespaces with not directly writable dict (GH-124667) #124758

Merged

serhiy-storchaka closed this as completed Sep 29, 2024

github-project-automation bot moved this to Doc issues in Argparse issues Sep 29, 2024

serhiy-storchaka added 3.12 only security fixes 3.13 bugs and security fixes 3.14 bugs and security fixes labels Sep 29, 2024

tacaswell mentioned this issue Oct 29, 2024

experimental jit causes infinite loops on 3.13 branch #126127

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argparse: parse_args with a subparser + namespace tries to setdefault on a mappingproxy object #116850

argparse: parse_args with a subparser + namespace tries to setdefault on a mappingproxy object #116850

alex-tianhuang commented Mar 15, 2024 •

edited by bedevere-app bot

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mimros commented May 14, 2024

argparse: parse_args with a subparser + namespace tries to setdefault on a mappingproxy object #116850

argparse: parse_args with a subparser + namespace tries to setdefault on a mappingproxy object #116850

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alex-tianhuang commented Mar 15, 2024 • edited by bedevere-app bot Loading

Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

Linked PRs

mimros commented May 14, 2024

alex-tianhuang commented Mar 15, 2024 •

edited by bedevere-app bot

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