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Inconsistent name mangling in TypedDict in function and class forms #129567
Description
Bug report
Let's say that you have a dict like {"__key": 1} and you want to type it.
You can write:
>>> import typing
>>> class A(typing.TypedDict):
... __key: int
>>> A.__mutable_keys__
frozenset({'_A__key'})and:
>>> B = typing.TypedDict("B", [("__key", int)])
>>> B.__mutable_keys__
frozenset({'__key'})Note that A mangles __key as a regular name. While B does not.
I guess that it is expected, but!
Docs (https://docs.python.org/3/library/typing.html#typing.TypedDict) does not say anything about this behavior. We only mention that functional form should be used for invalid identifiers. But, __key is a valid indentifier.
We don't have explicit tests for this either.
And Typing Spec does not mention this as well: https://typing.readthedocs.io/en/latest/spec/typeddict.html
So, what we can do:
- Do not mangle names in this case (hard and problematic: it can break existing stuff)
- Document and test current behavior (my vote)
Please, share your thoughts on this. And I willing to send a PR with the fix.
Activity
picnixz commentedon Feb 2, 2025
I'm +1 for documenting this and linking to the section about mangling so that users know how to write a mangling/demangling helper if needs arise (if they don't want to use the functional syntax)
Fix `IntrospectionQuery` type definition
Refactor `_StoreCallSig` to inline form
pythongh-129567: Add a note to `typing.TypedDict` docs about name man…
gh-129567: Add a note to `typing.TypedDict` docs about name mangling (#…
pythongh-129567: Add a note to `typing.TypedDict` docs about name man…
[3.13] gh-129567: Add a note to `typing.TypedDict` docs about name ma…
[3.12] pythongh-129567: Add a note to typing.TypedDict docs about nam…
[3.12] gh-129567: Add a note to typing.TypedDict docs about name mang…
ZeroIntensity commentedon Mar 21, 2025
This looks done :)