生成器

#生成器函数，函数里只要有yield关键字
def gen_func():
    yield 1
    yield 2
    yield 3

def fib(index):
    if index <= 2:
        return 1
    else:
        return fib(index-1) + fib(index-2)

def fib2(index):
    re_list = []
    n,a,b = 0,0,1
    while n<index:
        re_list.append(b)
        a,b = b, a+b
        n += 1
    return re_list

def gen_fib(index):
    n,a,b = 0,0,1
    while n<index:
        yield b
        a,b = b, a+b
        n += 1

for data in gen_fib(10):
    print (data)
# print (gen_fib(10))
# 斐波拉契 0 1 1 2 3 5 8
#惰性求值， 延迟求值提供了可能

def func():
    return 1

if __name__ == "__main__":
    #生成器对象， python编译字节码的时候就产生了，
    gen = gen_func()
    for value in gen:
        print (value)
    # re = func()
    # pass