python 关于嵌套循环以及循环内break的高级技巧

            
              from itertools import product,takewhile

a = [1,2,3]
b = [1,2,3]
c = [1,2,3]

#嵌套循环，当满足某个条件时执行
for aa,bb,cc in product(a,b,c):
    if aa+bb+cc == 9:
        print(aa,bb,cc)


#自定义一个方法，返回真则继续，不为真则break
def check_num(num):
    if num<3:
        return True
    return False

for i in takewhile(check_num,a):
    print(i)