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python - How is hash(None) calculated?

On my machine, hash(None) returns a value:

>>> hash(None)
-2138947203

Just out of curiosity, how is this hash value calculated? It doesn't seem as though this value is based on None's id as it is the same if I restart the Python interpreter.

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It is based on None's id, but None is one of a few Python objects that are defined as C global variables, so its address (typically) doesn't change between Python runs. Other such objects are True and False (but these are hashed as ints), or built-in classes like object and tuple.

The address (and hash) is different between different CPython builds, however. On my system, hash(None) gives 539708.


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