gh-143831: Compare cells by identity in forward references #143848
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abhinand-c
reviewed
Jan 15, 2026
| self.__forward_is_class__, | ||
| tuple(sorted(self.__cell__.items())) if isinstance(self.__cell__, dict) else self.__cell__, | ||
| ( # cells are mutable and not hashable as well | ||
| tuple(sorted([(name, id(cell)) for name, cell in self.__cell__.items()])) |
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@johnslavik Do we need the list comprehension here? We could pass a generator directly to sorted() for slightly better efficiency:
tuple(sorted((name, id(cell)) for name, cell in self.__cell__.items()))Also, is there any way to avoid sorting altogether without compromising the stability or correctness of the hash?
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Cells are mutable and, in regular comparison, they are equal when their contents are equal (or if both are empty).
Two different cells should not be considered equal by value in forward references, though.
If there are two separate cells, they either (1) target different variables or (2) belong to different scopes, so two separate forward references storing two separate cells are conceptually unequal even if these cells happen to be equal at a given point in time. Mutability, essentially.
I'm still working on tests.
TypeError: unhashable type: 'cell'#143831