[python学习]利用generator实现杨辉三角

杨辉三角定义如下：


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

目的：把每一行看做一个LIST，编写一个generator,然后不断输出下一行

代码：

def triangles():

 L = [1]
    a = 1
    while True:
       try:
           if a == 1:
              yield L
           else:
              L = [L[i-1] + L[i] for i in range(1, a-1)]
              L=[1]+L+[1]
              yield L
           a+=1
       except:
          print('error')
          break

调用：

n = 0
for t in triangles():
    print(t)
    n = n + 1
    if n == 10:
        break

输出结果：

[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]
error