asyncio使用事件（Event）处理通知 Python asyncio.Event

asyncio Event事件旨在向多个协程发出信号，因此协程方法可被阻塞，直到Event被“设置”为止。

使用事件循环构建一个清理模式：

import asyncio
import logging
import random

logging.basicConfig(level=logging.INFO)


async def busy_loop(interval, work, worker, shutdown_event):
    """持续工作，直到shutdown_event被设置"""
    while not shutdown_event.is_set():
        await worker(work)
        await asyncio.sleep(interval)
    logging.info('shutdown event set, exit busy_loop')
    return work


async def cleanup(mess, shutdown_event):
    """阻塞等待shutdown_event被设置，然后清理mess垃圾"""
    await shutdown_event.wait()
    logging.info('cleaning up the mess(脏东西/粪便): %s', mess)
    # 在这里添加清理逻辑


async def shutdown(delay, shutdown_event):
    """阻塞等待delay秒，然后设置shutdown_event"""
    await asyncio.sleep(delay)
    shutdown_event.set()


async def add_mess(mess_pile, ):
    """向mess_pile垃圾堆中添加一个mess垃圾"""
    mess = random.randint(1, 100)
    logging.info('adding mess: %s', mess)
    mess_pile.append(mess)


async def main():
    shutdown_event = asyncio.Event()
    shutdown_delay = 10
    work = []
    await asyncio.gather(*[shutdown(shutdown_delay, shutdown_event),
                           cleanup(work, shutdown_event),
                           busy_loop(1, work, add_mess, shutdown_event)])


asyncio.run(main())

打印
INFO:root:adding mess: 43
INFO:root:adding mess: 43
INFO:root:adding mess: 78
INFO:root:adding mess: 18
INFO:root:adding mess: 68
INFO:root:adding mess: 34
INFO:root:adding mess: 2
INFO:root:adding mess: 77
INFO:root:adding mess: 54
INFO:root:adding mess: 21
INFO:root:cleaning up the mess(脏东西/粪便): [43, 43, 78, 18, 68, 34, 2, 77, 54, 21]
INFO:root:shutdown event set, exit busy_loop

知识点：

• event.is_set 通知正在等待或者检查状态的协程
• event.wait() 协程来等待Event被event.set()设置

补充：

• event.clear() 清除is_set()的状态，变为未设置的状态