Python: Diff the dictionary

dictionaryDiffer.py

#!/usr/bin/python
class DictDiffer(object):
    """
    Calculate the difference between two dictionaries as:
    (1) items intersected
    (2) items added
    (3) items removed
    (4) keys same in both but changed values
    (5) keys same in both and unchanged values
    """
    def __init__(self, baseDic, dic):
        self.baseDic, self.dic = baseDic, dic
        self.baseDicSet, self.dicSet = set(baseDic.keys()), set(dic.keys())
        self.intersection = self.baseDicSet.intersection(self.dicSet)
    def intersected(self):
        return self.intersection
    def added(self):
        return self.dicSet - self.intersection
    def removed(self):
        return self.baseDicSet - self.intersection
    def changed(self):
        return set(i for i in self.intersection if self.baseDic[i] != self.dic[i])
    def unchanged(self):
        return set(i for i in self.intersection if self.baseDic[i] == self.dic[i])

dic1 = {'a': 1, 'b': 3, 'c': 0, 'e':5, 'x':99, 'z':8}
dic2 = {'a': 1, 'b': 6, 'd': 0, 'f':7, 'x':99, 'y':45}
d = DictDiffer(dic1, dic2)
print "intersected:", d.intersected()   # set(['a', 'b', 'x'])
print "Added:", d.added()               # set(['d', 'f', 'y'])
print "removed:", d.removed()           # set(['c', 'e', 'z'])
print "changed:", d.changed()           # set(['b'])
print "unchanged:", d.unchanged()       # set(['a', 'x'])