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gh-135228: Create __dict__ and __weakref__ descriptors for object #136966

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gh-135228: Create __dict__ and __weakref__ descriptors for object #136966

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@encukou encukou commented Jul 22, 2025 •
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Here's another possible way to solve #135228:
The __dict__ and __weakref__ descriptors don't really need to hold a strong reference to "their" type; they are generic and could be created for object instead.
Here's a proof of concept. A cleaner way to do this would be creating the descriptor objects once and caching them in the interpreter state.

This does involve a behaviour change -- before:

>>> class C: pass
>>> C.__dict__['__dict__']
<attribute '__dict__' of 'C' objects>
>>> C.__dict__['__dict__'].__objclass__
<class '__main__.C'>

After:

>>> class C: pass
>>> C.__dict__['__dict__']
<attribute '__dict__' of 'object' objects>
>>> C.__dict__['__dict__'].__objclass__
<class 'object'>

JelleZijlstra and others added 5 commits July 20, 2025 16:57
@JelleZijlstra
pythongh-135228: When @DataClass(slots=True) replaces a dataclass, ma…
027f629 
…ke the original class collectible

An interesting hack, but more localized in scope than python#135230.

This may be a breaking change if people intentionally keep the original class around
when using `@dataclass(slots=True)`, and then use `__dict__` or `__weakref__` on the
original class.
@encukou
Keep just the test
c82d86b
@encukou
Create __dict__ and __weakref__ descriptors for object
9ef8632
@encukou
Adjust internals of inspect.getattr_static
696f1d0
@encukou
Merge in the main branch
58c7a39
@bedevere-app bedevere-app bot mentioned this pull request Jul 22, 2025
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serhiy-storchaka
serhiy-storchaka reviewed Jul 22, 2025
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@encukou
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encukou commented Jul 22, 2025

I can polish this, but I think it'd be better to target 3.15, and follow through a bit more.
The descriptor objects themselves could be shared across all classes that need them (within an interpreter), but it's not as straightforward to plug that into the type creation machinery.

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encukou commented Jul 30, 2025

Here's a polished version: the descriptors are made for type, which means thet skip type-checking (they work on any object). The getter/setter functions already check if their argument has a __dict__/__weakref__.

And since they're the same for all objects, they can be shared across all types in an interpreter -- that is, cached in interpreter state.

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