python 推导式可用在三种结构上，列表、集合和字典

list 列表

if_list = [x for x in range(0, 10) if x %2 != 0] # [1, 3, 5, 7, 9]
mulit_list = [x + y for x in range(0,5) for y in range(0,2)] # [0, 1, 1, 2, 2, 3, 3, 4, 4, 5] 相当于双层for循环

map 集合元素唯一,无序

map = {x for x in ['a', 'b', 'c', 'a']}
print(map) # {'b', 'a', 'c'}

dict 字典

dict1 = dict((id, x) for id, x in enumerate(['a', 'b', 'c', 'a'])) # {0: 'a', 1: 'b', 2: 'c', 3: 'a'}