生成器

# 生成器

g = (i * i for i in range(10) if i % 2 == 0)
for i in g:
    print(i)


# 用生成器实现斐波拉契数列

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

for i in fib(10):
    print(i)

# 用生成器实现杨辉三角

def pascal_triangle():
    L = [1]
    while 1:
        yield L
        L.append(0)    # 卧槽，这点完全想不到！
        L = [L[i - 1] + L[i] for i in range(len(L))]

n = 0
for i in pascal_triangle():
    print(i)
    n+=1
    if n == 10:
        break