Python asyncio:读者回调和协同通信

Question

我试图实现一个简单的想法,将数据从stdin传递到协程:

import asyncio
import sys

event = asyncio.Event()

def handle_stdin():
    data = sys.stdin.readline()
    event.data = data  # NOTE: data assigned to the event object
    event.set()

@asyncio.coroutine
def tick():
    while 1:
        print('Tick')
        yield from asyncio.sleep(1)

        if event.is_set():
            data = event.data  # NOTE: data read from the event object
            print('Data received: {}'.format(data))
            event.clear()

def main(): 
    loop = asyncio.get_event_loop()
    loop.add_reader(sys.stdin, handle_stdin)
    loop.run_until_complete(tick())    

if __name__ == '__main__':
    main()

这段代码工作正常,但是带有变量而不是Event对象的简化版本也适用:

data = None

def handle_stdin():
    global data
    data = sys.stdin.readline()

@asyncio.coroutine
def tick():
    while 1:
        print('Tick')
        yield from asyncio.sleep(1)

        global data
        if data is not None:
            print('Data received: {}'.format(data))
            data = None

我的问题是:方法Event是否正确？或者有更好的方法与另一个asyncio对象来处理这种问题？那么,如果方法Event很好,使用变量也可以吗？

谢谢.

Answer 1

我认为asyncio.Queue更适合这种生产者/消费者关系:

import asyncio
import sys

queue = asyncio.Queue()

def handle_stdin():
    data = sys.stdin.readline()
    # Queue.put is a coroutine, so you can't call it directly.
    asyncio.async(queue.put(data)) 
    # Alternatively, Queue.put_nowait() is not a coroutine, so it can be called directly.
    # queue.put_nowait(data)

async def tick():
    while 1:
        data = await queue.get()
        print('Data received: {}'.format(data))

def main(): 
    loop = asyncio.get_event_loop()
    loop.add_reader(sys.stdin, handle_stdin)
    loop.run_until_complete(tick())    

if __name__ == '__main__':
    main()

涉及的逻辑少于a Event,你需要确保正确设置/取消设置,并且不需要sleep唤醒,检查,返回睡眠,循环,就像使用全局变量一样.因此,该Queue方法更简单,更小,并且阻止事件循环比其他可能的解决方案更少.其他解决方案在技术上是正确的,因为它们将正常运行(只要你不在yield fromif if event.is_set()和if data is not None:block中引入任何调用).他们只是有点笨重.