python中的map,collections,copy函数

l = [ [1,2,3], [2,3,4] ]

map(list,*l)

for row in map(list,zip(*l)):

print(row)

结果[1, 2], [2, 3], [3, 4]

import collections

l = [1,2,1,2,3]

c = collections.Counter(l)

结果c = {'1':2,'2':2,'3':1}

s = 'apple'

collections.Counter(s)

{'a':1, 'p':2, 'l':1, 'e':1}

import copy

a = [1,2]

b = copy.deepcopy(a)

复制的列表和原列表不会相互影响