python 的小技巧之统计list里面元素的个数

一般写法

def  count_list(std:list,tongji):

    i=0

    for item in std:

        if item==tongji:

            i+=1

    print(i)

if __name__=='__main__':

    lists=[1,2,3,4,5,1,2,3,4,5,2,2,2,3,4]

    count_list(std=lists,tongji=2)

新写法， python 3.5 之后

def  count_list(std:list,tongji):

    from collections import Counter

    name=Counter()

    for  num in std:

        name[num]+=1

    print(name[tongji])

if __name__=='__main__':

    lists=[1,2,3,4,5,1,2,3,4,5,2,2,2,3,4]

    count_list(std=lists,tongji=2)

少了一个if判断，而且 一次可以获取列表所有元素的个数