python dictionary: KeyError but the key exists when iterating

Question

nobj = Name.lookup(self.name)
for k,v in Animal.animals_of.iteritems():
        if k == nobj:
            print 'found %s with %s' % ( nobj, k)
            print v

print Animal.animals_of[nobj]

OUTPUT:

found abc with abc
[<Animal object at 0x7f9b00aa2290>]

   print Animal.animals_of[nobj]
KeyError: <Name object at 0x7f9afe5824d0>

Question:
when i am iterating through Animal.animals_of, i can find nobj.

But when i am doing a lookup on nobj , it cant find it

Animal obj has its own __cmp__.
Does python dictionary use different compare method or something?