asyncio中的task

取消asyncio中的task

run_until_complete()和run_forever()

run_until_complete() ，tasks运行完成时会停止loop，run_forever()则不会
在平时使用asyncio时遇到某些异常需要停止task，比如数据库插入表出错时出错需要停止后面task

import asyncio
import time


async def get_html(sleep_time):
    print("waiting")
    await asyncio.sleep(sleep_time)
    print(f"done after {sleep_time}s")


if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    task1 = get_html(2)
    task2 = get_html(3)
    task3 = get_html(4)
    tasks = [task1, task2, task3]
    try:
        loop.run_until_complete(asyncio.gather(*tasks))
    except KeyboardInterrupt as e:  # 当在终端按下Ctrl+c时产生的异常 模拟异常产生时
        all_tasks = asyncio.Task.all_tasks()  # 获取所有tasks
        for task in all_tasks:
            print('cancel task')
            print(task.cancel())  # 取消task任务
        loop.stop()
        loop.run_forever() # run_forever没写的话可能会出现异常，可能与python版本有关
    finally:
        loop.close()

协程之间的调用

import asyncio

async def compute(x, y):
    print("Compute %s + %s ..." % (x, y))
    await asyncio.sleep(1.0)
    return x + y

async def print_sum(x, y):
    result = await compute(x, y)
    print("%s + %s = %s" % (x, y, result))

loop = asyncio.get_event_loop()
loop.run_until_complete(print_sum(1, 2))
loop.close()

下面时时序图