【Python入门学习】列表生成和函数生成器的方式实现杨辉三角

列表生成：

L = [i for i in range(10)]

列表生成器：

g = (i for i in range(10))

函数生成器使用的关键字yield实现

例如fib生成器

1 def fib(max):
2 n, a, b = 0, 0, 1
3 while n < max:
4 #print(b)
5 yield b
6 a, b = b, a + b
7 n = n + 1
8 return 'done'

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

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

1 def triangles():
2 n = 0
3 L1 = [1]
4 L2 = [1, 1]
5 L = []
6 while True:
7 n += 1
8 if n == 1:
9 L = L1
10 elif n == 2:
11 L = L2
12 yield L
13 L = [L[i] + L[i+1] for i in range(len(L) - 1)]
14 L.insert(0, 1)
15 L.append(1)
16
17 n = 0
18 results = []
19 for t in triangles():
20 print(t)
21 results.append(t)
22 n = n + 1
23 if n == 10:
24 break
25
26 if results == [
27 [1],
28 [1, 1],
29 [1, 2, 1],
30 [1, 3, 3, 1],
31 [1, 4, 6, 4, 1],
32 [1, 5, 10, 10, 5, 1],
33 [1, 6, 15, 20, 15, 6, 1],
34 [1, 7, 21, 35, 35, 21, 7, 1],
35 [1, 8, 28, 56, 70, 56, 28, 8, 1],
36 [1, 9, 36, 84, 126, 126, 84, 36, 9, 1]
37 ]:
38 print('测试通过!')
39 else:
40 print('测试失败!')