python - 在 Python 中将数据发送到生成器

Question

我的目标是了解向 Python 生成器发送数据的概念。下面是我的代码片段和意外的输出:

def spam():
    while True:
        received = yield
        print("Message received from generator function:", received)
        yield received


if __name__ == "__main__":
    s = spam()
    print(s)
    next(s)
    names = ["Bob", "Nancy", "Daniela", "Martin"]
    for name in names:
        print(s.send(name))

输出:

7tvmb228:Own subhayan.bhattachary$ python test_generators.py 
<generator object spam at 0x10873aa20>
Message received from generator function: Bob
Bob
None
Message received from generator function: Daniela
Daniela
None

有人可以指出 None 值来自哪里以及如何解决这个问题。我的假设是，值不会传递给函数。但为什么会这样呢。我哪里出错了。

感谢您的提前答复。

Answer 1

None 值来自 received = Yield，这本质上意味着您正在生成 None 值。您的 spam() 函数中只需要有一个 yield:

def spam():
    received = None
    while True:
        received = yield received
        print("Message received from generator function:", received)


if __name__ == "__main__":
    s = spam()
    print(s)
    next(s)
    names = ["Bob", "Nancy", "Daniela", "Martin"]
    for name in names:
        print(s.send(name))

打印:

<generator object spam at 0x7f1518c8f9e8>
Message received from generator function: Bob
Bob
Message received from generator function: Nancy
Nancy
Message received from generator function: Daniela
Daniela
Message received from generator function: Martin
Martin