Why does None belong to immutable types?

In Python, the None object is immutable because its state cannot be changed after creation. None is a singleton, the only instance of the NoneType, which represents the absence of a value.

Immutability means that you cannot change the internal state of the object, for example, you cannot modify its attributes or contents. This is important for the safety and predictability of the code: if None could be changed, it could lead to errors and unpredictable behavior.

Example:

print(id(None))
# Attempting to modify None is impossible
# None.some_attr = 1  # will raise AttributeError

Thus, None is an immutable object that serves as a universal indicator of the absence of a value.