16、列表推导式

#列表中每个数值乘三
vec = [2,4,6]
print([3*x for x in vec])  #[6, 12, 18]

#if过滤器
print([3*x for x in vec if x > 3]) #[12, 18]

#嵌套

var1 = [1,2,3]
var2 = [4,5,6]
print([x*y for x in var1 for y in var2]) #[4, 5, 6, 8, 10, 12, 12, 15, 18]