异步队列的奇怪行为

Question

为什么 asyncio 队列在这里表现得如此奇怪，即使在那里放了一个项目它也显示为空？

In [1]: from multiprocessing import Queue

In [2]: q = Queue()

In [3]: q.empty()
Out[3]: True

In [4]: q.put(100)

In [5]: q.empty()
Out[5]: False

In [6]: from asyncio import Queue

In [7]: q = Queue()

In [8]: q.empty()
Out[8]: True

In [9]: q.put(100)
Out[9]: <generator object Queue.put at 0x7f97849bafc0>

In [10]: q.empty()
Out[10]: True

Answer 1

因为你什么都没放:

q.put(100)

put 这里 - 不是一个简单的函数，它是一个 coroutine. You should await 它将项目放入队列。

例如：

import asyncio
from asyncio import Queue


async def main():
    q = Queue()

    print(q.empty())  # True

    await q.put(100)

    print(q.empty())  # False


if __name__ ==  '__main__':
    loop = asyncio.get_event_loop()
    try:
        loop.run_until_complete(main())
    finally:
        loop.run_until_complete(loop.shutdown_asyncgens())
        loop.close()

Answer 2

作为 Mikhail Gerasimov 的回答，q.put(100) 是 coroutine 并解释更多细节...

Calling a coroutine does not start its code running – the coroutine object returned by the call doesn’t do anything until you schedule its execution. There are two basic ways to start it running: call await coroutine or yield from coroutine from another coroutine (assuming the other coroutine is already running!), or schedule its execution using the ensure_future() function or the AbstractEventLoop.create_task() method.

Coroutines (and tasks) can only run when the event loop is running.

来自Python Coroutines doc.

在 Mikhail Gerasimov 的示例中，另一个coroutineasync def main()用coroutineq.put(100)调用await，事件循环是运行loop.run_until_complete(main())如上面的描述

异步队列的奇怪行为

Weird behaviour of asyncio Queue

queue

python-asyncio

python-3.6