why dict objects are unhashable in python?

Question

I mean why cant we put key of dict as dict?

that means we can\'t have dictionary having key as another dictionary...

Answer 1

As others have said, the hash value of a dict changes as the contents change.

However if you really need to use dicts as keys, you can subclass dict to make a hashable version.

>>> class hashabledict(dict):
...    def __hash__(self):
...        return id(self)
... 
>>> hd = hashabledict()
>>> d = dict()
>>> d[hd] = "foo"
>>> d
{{}: 'foo'}

>>> hd["hello"] = "world"
>>> d
{{'hello': 'world'}: 'foo'}

This replaces the hash value used for the dict with the object's address in memory.