杨辉三角算法

# -*- coding: utf-8 -*-
def triangles():
    n = 0
    L = [1]
    while n < 20:
        yield L
        L = [1] + [L[i] + L[i+1] for i in range(n)] + [1] # n =0 时，循环语句【L[i] + L[i+1]】根本不会执行，所以不会报错
        n = n + 1

# 打印
for i in triangles():
    print(i)