之前写 Python 时，要比较两个字典的差异，自己写的比较 Low，然后在 github 上发现一个不错的类库，拿来就用了。

github: https://github.com/hughdbrown/dictdiffer

我的代码示例：

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.current_keys, self.past_keys = set(current_dict.keys()), set(past_dict.keys())
        self.intersect = self.current_keys.intersection(self.past_keys)

    def added(self):
        """ Find keys that have been added """
        return self.current_keys - self.intersect

    def removed(self):
        """ Find keys that have been removed """
        return self.past_keys - self.intersect

    def changed(self):
        """ Find keys that have been changed """
        return set(o for o in self.intersect
                   if self.past_dict[o] != self.current_dict[o])

    def unchanged(self):
        """ Find keys that are unchanged """
        return set(o for o in self.intersect
                   if self.past_dict[o] == self.current_dict[o])

    def new_or_changed(self):
        """ Find keys that are new or changed """
        # return set(k for k, v in self.current_dict.items()
        #           if k not in self.past_keys or v != self.past_dict[k])
        return self.added().union(self.changed())


var1 = {'a': 1, 'b': 1, 'c': 0}
var2 = {'a': 1, 'b': 2, 'd': 3, 'e': 4}
c = DictDiffer(var2, var1)
print('增加', c.added())
print('减少', c.removed())
print('变更', c.changed())

# 测试
# python dictdiff.py 
#增加 {'e', 'd'}
#减少 {'c'}
#变更 {'b'}