【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

def fib(max):
    n, a, b = 0, 0, 1
    while n < max:
	#print(b)
        yield b
        a, b = b, a + b
        n = n + 1
    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：

def triangles():
    n = 0
    L1 = [1]
    L2 = [1, 1]
    L = []
    while True:
        n += 1
        if n == 1:
            L = L1
        elif n == 2:
            L = L2
        yield L
        L = [L[i] + L[i+1] for i in range(len(L) - 1)]
        L.insert(0, 1)
        L.append(1)

n = 0
results = []
for t in triangles():
    print(t)
    results.append(t)
    n = n + 1
    if n == 10:
        break

if results == [
    [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]
]:
    print('测试通过!')
else:
    print('测试失败!')