gistfile1.txt

import collections

class TransformedDict(collections.MutableMapping):
    def __init__(self, *args, **kwargs):
        self.store = dict()
        self.update(dict(*args, **kwargs))  # use the free update to set keys

    def __getitem__(self, key):
        return self.store[self.__keytransform__(key)]

    def __setitem__(self, key, value):
        self.store[self.__keytransform__(key)] = value

    def __delitem__(self, key):
        del self.store[self.__keytransform__(key)]

    def __iter__(self):
        return iter(self.store)

    def __len__(self):
        return len(self.store)

    def __keytransform__(self, key):
        return key



class NodesDict(TransformedDict):
    def add(self, element):
        return self.__setitem__(element, element)  

    def __keytransform__(self, key):
        try:
            # now uniq for hash is only hwaddr key
            print 'hwaddr = ' + key['hwaddr']
            return key['hwaddr'] 
        except KeyError:
            print "Error: hwaddr not in key"
            raise() 

compute1 = dict() 
compute1['hwaddr'] = 'compute1_hwaddr'

compute2 = dict() 
compute2['hwaddr'] = 'compute2_hwaddr'

compute3 = dict() 
compute3['hwaddr'] = 'compute2_hwaddr' # duplicate hwaddr 

nodes = NodesDict();

nodes.add(compute1)
nodes.add(compute2)

print nodes.__len__()

Are you lost smth like that?

nodes.add(compute3)

yeah, right