第二模块 3.13 生成器

在Python中，这种一边循环一边计算后面元素的机制，称为生成器：generator。

>>> g= (x*x for x in range(10))
>>> next(g)
0
>>> 
>>> next(g)
1
>>> next(g)
4
>>> next(g)
9
>>> next(g)
16

a = 0
b = 1
count = 0
while count < 20:
    tmp = a  # 给新的a 赋值前 先把旧值存下来
    a = b  # 新的a = 1
    b = tmp+ b
    print(a,b)
    count +=1

def fib(n):
    a = 0
    b = 1
    count = 0
    while count < n:
        tmp = a  # 给新的a 赋值前 先把旧值存下来
        a = b  # 新的a = 1
        b = tmp + b
        #print( b)
        yield b  # 暂停
        count += 1
f = fib(20)
print(next(f))
print(next(f))
print(next(f))
print(next(f))