How to use custom type as dictionary key in Python

The Python dict documentation defines these requirements on key objects, i.e. they must be hashable.

Steps :

Implement a custom key class  and override hash and equality function.

e.g.

class CustomDictKey(object):

    def __init__(self, 

                 param1,

                 param2):

    

                self._param1 = param1

                self._param2 = param2

              

    def __hash__(self):

        return hash((self._param1,

                 self._param2))

    def __eq__(self, other):

        return ( ( self._param1,

                 self._param2 ) == ( other._param1,

                 other._param2) )

                

    def __str__(self):

        return "param 1: {0} param 2: {1}  ".format(self._param1, self._param2)

if __name__ == '__main__':

    # create custom key

    k1  = CustomDictKey(10,5)

    

    k2  = CustomDictKey (2, 4)

    

    dictionary = {}

    

    #insert elements in dictionary with custom key

    dictionary[k1] = 10

    dictionary[k2] = 20

    

    # access dictionary values with custom keys and print values

    print "key: ", k1, "val :", dictionary[k1]

    print "key: ", k2, "val :", dictionary[k2]