Understanding Immortal Objects in Python 3.12

Understanding Immortal Objects in Python 3.12

Abhinav Upadhyay provides a clear and detailed explanation of immortal objects coming in Python 3.12, which ensure Python no-longer updates reference counts for immutable objects such as True, False, None and low-values integers. The trick (which maintains ABI compatibility) is pretty simple: a reference count value of 4294967295 now means an object is immortal, and the existing Py_INCREF and Py_DECREF macros have been updated to take that into account.

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