Set of Dictionary

[Piet van Oostrum]

>>>>> Vibha Tripathi <vibtrip at yahoo.com> (VT) wrote:

>VT> Hi Folks,
>VT> I know sets have been implemented using dictionary but
>VT> I absolutely need to have a set of dictionaries...any
>VT> ideas how to do that?

A set cannot contain duplicates. What happens when one of the dictionaries
in the set is modified in such a way that it becomes equal to another
element?

Maybe you just need a list of dictionaries? Or maybe you want immutable
dictionaries to put in the set. In  that case you can define your own
immutable dictionary class that defines a hash function. Ideally you would
redefine the dictionary modification methods to make them generate error
messages. For safety in the following code a copy is made of the dict. 

The values in the dict must be hashable, which usually means immutable.

class immdict(dict):
    def __init__(self, somedict):
        self.data = somedict.copy()
        
    def __hash__(self):
        result = 0
        for elt in self.data:
            result ^= hash(elt) ^ hash(self.data[elt])
        return result

    def __repr__(self):
        return repr(self.data)
    __str__ = __repr__

d = immdict({1:0, 2:3})
s = Set()
s.add(d)
-- 
Piet van Oostrum <piet at cs.uu.nl>
URL: http://www.cs.uu.nl/~piet [PGP]
Private email: piet at vanoostrum.org