python 基础系列09-推导式

# python 基础系列09-推导式

# 引入sys库
import sys
import copy
from functools import reduce

if __name__ == '__main__':
    mylist = [1,2,3,4]
    # var * var 代表操作
    new_list = [var * var for var in  mylist]
    print(new_list) #[1, 4, 9, 16]

    #还可以过滤
    new_list2 = [var * var for var in mylist if var != 3]
    #注意
    new_list3 = (var * var for var in mylist if var != 3)
    print(new_list3)
    print(new_list3.__next__()) #取第一个值
    print(new_list3.__next__())
    print(new_list3.__next__())

    mylist2 = [1, 2, 3, 4]
    mydict = {var: 'a' for var in mylist2} #{1: 'a', 2: 'a', 3: 'a', 4: 'a'}
    print(mydict)
    mydict = {var: 'a' for var in mylist2 if var > 3}

    #集合操作
    myset = {var+1 for var in mylist2 }
    print(myset)