将Counter与列表一起使用

Question

我如何使用集合库中的计数器将列表列表转换为每个单词整体出现次数的计数？

例如 [['a','b','a','c'], ['a','b','c','d']] -> {a:2, b:2, c:2, d:1}

即a,b并且c发生在两个列表中但d仅发生在一个列表中.

Answer 1

使用生成器表达式set:

>>> from collections import Counter
>>> seq = [['a','b','a','c'], ['a','b','c','d']]
>>> Counter(x for xs in seq for x in set(xs))
Counter({'a': 2, 'c': 2, 'b': 2, 'd': 1})

响应评论,没有生成器表达式:

>>> c = Counter()
>>> for xs in seq:
...     for x in set(xs):
...         c[x] += 1
...
>>> c
Counter({'a': 2, 'c': 2, 'b': 2, 'd': 1})

Answer 2

from itertools import chain
from collections import Counter

seq = [['a','b','a','c'], ['a','b','c','d']]
c = Counter(chain(*seq))

print(c)
Counter({'a': 3, 'b': 2, 'c': 2, 'd': 1})