python dict diff

DictDiffer.py

class DictDiffer(object):
  """
  Calculate the difference between two dictionaries as:
  (1) items added
  (2) items removed
  (3) keys same in both but changed values
  (4) keys same in both and unchanged values
  
  http://code.activestate.com/recipes/576644-diff-two-dictionaries/#c7
  """
  def __init__(self, current_dict, past_dict):
    self.current_dict, self.past_dict = current_dict, past_dict
    self.set_current, self.set_past = set(current_dict.keys()), set(past_dict.keys())
    self.intersect = self.set_current.intersection(self.set_past)
  def added(self):
    return self.set_current - self.intersect
  def removed(self):
    return self.set_past - self.intersect
  def changed(self):
    return set(o for o in self.intersect if self.past_dict[o] != self.current_dict[o])
  def unchanged(self):
    return set(o for o in self.intersect if self.past_dict[o] == self.current_dict[o])