[tonghuaroot]

Python subclasses of uuid.UUID are allocated with PyType_GenericAlloc(), so cached_hash starts at 0 instead of -1 and __init__() never resets it. With the C implementation every subclass instance hashes to 0 and is not found next to an equal UUID in a set or dict:

import uuid
class MyUUID(uuid.UUID): pass
hash(MyUUID(int=1))                  # 0
uuid.UUID(int=1) in {MyUUID(int=1)}  # False

Calling __init__() or __setstate__() on an existing UUID also kept its old cached hash. Reset cached_hash in both. The C implementation is unreleased, so there is no NEWS entry.

• Issue: Implement UUID functions and type in C #139122