immutable (if the object's hash value changes, it will be in the wrong hash
bucket).
-
User-defined classes have :meth:`__eq__` and :meth:`__hash__` methods
by default; with them, all objects compare unequal (except with themselves)
and ``x.__hash__()`` returns an appropriate value such that ``x == y``
implies both that ``x is y`` and ``hash(x) == hash(y)``.
- .. impl-detail::
-
- CPython uses ``hash(id(x))`` as the default hash for class instances.
-
Classes which inherit a :meth:`__hash__` method from a parent class but
change the meaning of :meth:`__eq__` such that the hash value returned is no
longer appropriate (e.g. by switching to a value-based concept of equality