How to create an immutable dictionary in python?

Question

I want to subclass dict in python such that all the dictionaries of the sub-class are immutable.

I don't understand how does __hash__ affects the immutability, since in my understanding it just signifies the equality or non-equality of objects !

So, can __hash__ be used to implement immutability ? How ?

Update:

Objective is that common response from an API is available as a dict, which has to be shared as a global variable. So, that needs to be intact no matter what ?

Answer 1

I found a Official reference : suggestion contained in a rejected PEP.

class imdict(dict):
    def __hash__(self):
        return id(self)

    def _immutable(self, *args, **kws):
        raise TypeError('object is immutable')

    __setitem__ = _immutable
    __delitem__ = _immutable
    clear       = _immutable
    update      = _immutable
    setdefault  = _immutable
    pop         = _immutable
    popitem     = _immutable

Attribution : http://www.python.org/dev/peps/pep-0351/