AttributeError: 'ArgumentParser' object has no attribute 'title'

[khalfella]

Bug report

Bug description:

    some_parser = subparsers.add_parser('something',
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/argparse.py", line 1236, in add_parser
    parser = self._parser_class(**kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/argparse.py", line 1827, in __init__
    self._add_container_actions(parent)
  File "/usr/lib/python3.12/argparse.py", line 1568, in _add_container_actions
    cont = title_group_map[group._container.title]
                           ^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'ArgumentParser' object has no attribute 'title'

After updating to latest python version on gentoo Python 3.12.8 I started seeing this failure. This might be related to fix in GH-125210. Manually reverting this change fixed the issue for me.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

[khalfella]

@serhiy-storchaka @djsutherland - Can you please take a look at this? Thanks.

[hugovk]

@khalfella Please can you provide a complete and minimal snippet of code to reproduce this?

[khalfella]

import argparse

parser = argparse.ArgumentParser(description="foo", epilog="bar")
run_args = argparse.ArgumentParser()
plan_args = run_args.add_mutually_exclusive_group(required=False)
subparsers = parser.add_subparsers(dest='baz', title="sub", description="subparser")
some_parser = subparsers.add_parser('some_parser', parents=[plan_args])

Not good reproducer, but this is what I was able to extract from large code. Hopefully it helps.

It fails with

AttributeError: 'ArgumentParser' object has no attribute 'title'

Reverting the change makes it fail for a different reason.

argparse.ArgumentError: argument -h/--help: conflicting option strings: -h, --help

[serhiy-storchaka]

Thank you for your report @khalfella.

In 3.13 you get more specific error message:

TypeError: parents must be a list of ArgumentParser

plan_args in your example is a mutually exclusive group, not ArgumentParser. If this also is a case in your original code, it uses argparse incorrectly.

[khalfella]

Thanks @serhiy-storchaka for taking a look. Looks like the bug in our code that was uncovered by python update. I will go ahead and close this issue as no further work is needed.