【12.2】task取消和子协程调用原理

task取消

import asyncio
import time


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


if __name__ == '__main__':
    task1 = get_html(2)
    task2 = get_html(3)
    task3 = get_html(3)

    tasks = [task1, task2, task3]

    loop = asyncio.get_event_loop()

    try:
        loop.run_until_complete(asyncio.gather(*tasks))
    except KeyboardInterrupt as e:
        # KeyboardInterrupt 是按Ctrl+C终止程序时抛出的异常
        # 获取所有的task
        all_tasks = asyncio.Task.all_tasks()
        for task in all_tasks:
            print('cancel task')
            print(task.cancel())
        loop.stop()
        loop.run_forever()
    finally:
        loop.close()

waiting
waiting
waiting
cancel task
True
cancel task
True
cancel task
True