generator输出杨辉三角

杨辉三角定义如下：

          1        1   1      1   2   1    1   3   3   1  1   4   6   4   11   5   10  10  5   1

把每一行看做一个list，试写一个generator，不断输出下一行的list：

# 期待输出:# [1]# [1, 1]# [1, 2, 1]# [1, 3, 3, 1]# [1, 4, 6, 4, 1]# [1, 5, 10, 10, 5, 1]# [1, 6, 15, 20, 15, 6, 1]# [1, 7, 21, 35, 35, 21, 7, 1]# [1, 8, 28, 56, 70, 56, 28, 8, 1]# [1, 9, 36, 84, 126, 126, 84, 36, 9, 1]

def triangles():    L=[1]    yield L    while True:        L=[1]+[L[x]+L[x+1] for x in range(len(L)-1)]+[1]        yield Ln=0for L in triangles():    print(L)    n=n+1    if n==10:        break