__annotate__ functions generated by CPython for class methods have an incorrect __qualname__

Bug report

Bug description:

The __qualname__ of __annotate__ functions of methods of classes incorrectly refers to the __annotate__ function of the class itself.

class Example:
    x: int
    def func(self, x: int) -> str: ...

print(f"{Example.__annotate__.__qualname__ = }")
print(f"{Example.func.__annotate__.__qualname__ = }")

Output:

Example.__annotate__.__qualname__ = 'Example.__annotate__'
Example.func.__annotate__.__qualname__ = 'Example.__annotate__'

CPython versions tested on:

3.14, CPython main branch

Operating systems tested on:

No response

Linked PRs

@JelleZijlstra

cc @JelleZijlstra

This is also similar for __annotate__ functions on global functions:

>>> def f() -> None: pass
... 
>>> f.__annotate__.__qualname__
'__annotate__'

Note arguably fixing this requires a magic number bump since it changes compiler output. Is this worth the disruption of a magic number bump? I'm not sure.

pythongh-137814: Fix `__qualname__` of `__annotate__`

See #143067 -- it breaks pickling.

Is this worth the disruption of a magic number bump? I'm not sure.

Just to provide a end-user feedback to give some particular context to the previous comment: on the scientific python side, we might have some parallel processing that would try to pickle some object coming from a class with annotations.

Not back-porting to 3.14 would mean that an entire library will not be compatible with a version of Python which looks strange I think.

Perhaps you can work around this by dropping the annotations before pickling? Do you really need the annotations in the parallel workers?

@JelleZijlstra

It looks something interesting to explore. I'll definitely have a look. Thanks @JelleZijlstra

pythongh-137814: [3.14] Fix __qualname__ of __annotate__ functions in…

I found an alternative fix that doesn't require bumping the magic number, so let's do that for 3.14: #148221.

#137842 is still the better long-term solution so I plan to land that for 3.15+.

gh-137814: Fix `__qualname__` of `__annotate__` (#137842)

[3.14] gh-137814: Fix __qualname__ of __annotate__ functions in the i…

This is now fixed on both 3.14 and main, though with different solutions.

Thanks a bunch.

pythongh-137814: Fix `__qualname__` of `__annotate__` (python#137842)

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`annotate` functions generated by CPython for class methods have an incorrect `qualname` #137814

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__annotate__ functions generated by CPython for class methods have an incorrect __qualname__ #137814

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Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

Linked PRs

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ZeroIntensity commented on Aug 15, 2025

JelleZijlstra commented on Aug 16, 2025

serhiy-storchaka commented on Dec 23, 2025

glemaitre commented on Apr 7, 2026

JelleZijlstra commented on Apr 7, 2026

glemaitre commented on Apr 7, 2026

JelleZijlstra commented on Apr 7, 2026

JelleZijlstra commented on Apr 16, 2026

glemaitre commented on Apr 16, 2026

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`annotate` functions generated by CPython for class methods have an incorrect `qualname` #137814