dictdiffer.py

# -*- coding: utf-8 -*-
'''
    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

    Originally posted at http://stackoverflow.com/questions/1165352/fast-comparison-between-two-python-dictionary/1165552#1165552
    Available at repository: https://github.com/hughdbrown/dictdiffer
'''

def diff(current_dict, past_dict):
    return DictDiffer(current_dict, past_dict)

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
    """

    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])