在一次操作中用两种方法对两个字典进行减法时寻找差异

Question

我有这个密码：

new = {'a': 1, 'b': 2}
old = {'a': 1, 'c': 3}
added = new.keys() - old.keys()
if added:
  print('{} keys have been added'.format(len(added)))
removed = old.keys() - new.keys()
if removed:
  print('{} keys have been removed'.format(len(removed)))
# added, removed = minus_dict(new, old)

我得做两次减法运算。是否存在负dict函数？我的意思是我如何找到更有效的方式添加和删除

Answer 1

如果单个集合足够，请使用XOR运算符：

>>> old.keys() ^ new.keys()
{'c', 'b'}

如果这还不够好，你就得做两次减法，或者自己编一个算法