python Counter ^

a = Counter([1,2,2,3]), b = Counter([1,2]) 我们现在要计算a^b，也就是a和b的交集，结果为：

>>> a = Counter([1,2,2,3]) >>> a Counter({2: 2, 1: 1, 3: 1}) >>> b = Counter([1,2]) >>> b Counter({1: 1, 2: 1}) >>> a&b Counter({1: 1, 2: 1})

由此，可以看出，取交集不仅针对key，还要针对val