AttributeError in 3.11 on repr() of enum member if the enum has a non-Enum EnumType parent

Bug report

In CPython 3.11.0 - 3.11.2 (but not 3.10.10), I get a weird AttributeError when repr() is called on an Enum member of a class that was defined using multiple inheritance. Minimal code to reproduce:

from enum import Enum, EnumMeta

class _EnumSuperClass(metaclass=EnumMeta):
    pass

class E(_EnumSuperClass, Enum):
    A=1

print(repr(E.A))

With Python up to 3.10, the output is:

<E.A: 1>

With Python 3.11, the output is:

Traceback (most recent call last):
  File "C:\devel\tmp\api\e.py", line 9, in <module>
    print(repr(E.A))
          ^^^^^^^^^
  File "C:\Program Files\Python311\Lib\enum.py", line 1169, in __repr__
    return "<%s.%s: %s>" % (self.__class__.__name__, self._name_, v_repr(self._value_))
                                                                  ^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Python311\Lib\enum.py", line 1168, in __repr__
    v_repr = self.__class__._value_repr_ or repr
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: type object 'int' has no attribute '_value_repr_'

Your environment

Python 3.11.0 (main, Oct 24 2022, 18:26:48) [MSC v.1933 64 bit (AMD64)] on win32
(But reproduced also on 3.11.2)

Linked PRs

Reproduced also on Linux in case it's important: Python 3.11.2 (main, Mar 1 2023, 14:46:02) [GCC 10.2.1 20210110] on linux

pythongh-102558: Fix AttributeError or repr() of enum member

Wow, this must be the fastest fix I've ever seen implemented in response to a random dude's complaint in the history of paid SLA contracts. Oh wait, I don't have any contract. Kudos and thanks.

pythongh-102558: Fix AttributeError or repr() of enum member

@ethanfurman

@ethanfurman
I submitted the patch but not sure it is the correct fix(closer to work around)
So please let me know if you have a better fix. (or you can direct fix this)

gh-102558: [Enum] fix AttributeError during member repr() (GH-102601)

pythongh-102558: [Enum] fix AttributeError during member repr() (pyth…

Merging in the work-around; will investigate further as time allows.

gh-102558: [Enum] fix AttributeError during member repr() (GH-102601)

@vashek

@vashek What is your actual use-case for that coding style? Making a non-Enum class with EnumMeta as the type is not the intended usage.

@ethanfurman

@ethanfurman Now I feel a bit silly, because it seems like I brought it upon myself completely needlessly and wasted your time. Sorry.

What I'm doing is I have a class with some class methods for enums, and then I'm mixing it into the actual enums. I guess when I did that, my thought process was "if I'm going to mix in another class into the enum, and the enum has a special metaclass, surely I can't just use an ordinary class with its ordinary metaclass -- surely the mixed-in classes must have a common metaclass". Now that I googled and read up on the subject, I think I now understand that this would have only been a problem if my base class used a different metaclass. I don't remember whether I had ever tried it without the metaclass -- maybe I haven't. I tried now and it seems to work fine.

I mean the fix is still nice, but I suppose the "bug" was only ever encountered by me and completely unnecessarily anyway, apparently.

No worries, glad it ended up being an easy fix for us both.

Thanks, looks like this was fixed and backported!

pythongh-102558: [Enum] fix AttributeError during member repr() (pyth…

gh-102558: [Enum] better handling of non-Enum EnumType classes (GH-10…

pythongh-102558: [Enum] better handling of non-Enum EnumType classes (p…

gh-102558: [Enum] better handling of non-Enum EnumType classes (GH-10…

pythongh-102558: [Enum] fix AttributeError during member repr() (pyth…

pythongh-102558: [Enum] better handling of non-Enum EnumType classes (p…

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AttributeError in 3.11 on repr() of enum member if the enum has a non-Enum EnumType parent #102558

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AttributeError in 3.11 on repr() of enum member if the enum has a non-Enum EnumType parent #102558

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vashek commented on Mar 9, 2023

vashek commented on Mar 9, 2023

corona10 commented on Mar 11, 2023

ethanfurman commented on Mar 23, 2023

ethanfurman commented on Mar 25, 2023

vashek commented on Mar 25, 2023

ethanfurman commented on Mar 25, 2023

hauntsaninja commented on Mar 25, 2023

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