import asyncio
import time

async def say_after(delay, what):
    print(f'[%s]: starting %s' % (time.time(), what))
    await asyncio.sleep(delay)
    print(f'[%s]: ending %s' % (time.time(), what))


async def main():
    task1 = asyncio.create_task(
        say_after(1, 'hello'))

    task2 = asyncio.create_task(
        say_after(2, 'world'))

    task3 = asyncio.create_task(
        say_after(0.5, 'Hai')
    )

    print(f"started at {time.strftime('%X')}")

    # Wait until both tasks are completed (should take
    # around 2 seconds.)
    await task1
    # await task2

    print(f"finished at {time.strftime('%X')}")


if __name__ == '__main__':
    asyncio.run(main())

started at 11:49:41
[1691380181.884058]: starting hello
[1691380181.884095]: starting world
[1691380181.884105]: starting Hai
[1691380182.385623]: ending Hai
[1691380182.885086]: ending hello
finished at 11:49:42

create_task 会顺序把三个任务放入队列。 await 相当于一把发令枪，trigger 一下，三个任务顺序开始执行。

如果此时，在 await task1 之后，再 sleep 一下，就能看到执行时间最长的那个任务也结束了。

import asyncio
import time

async def say_after(delay, what):
    print(f'[%s]: starting %s' % (time.time(), what))
    await asyncio.sleep(delay)
    print(f'[%s]: ending %s' % (time.time(), what))


async def main():
    task1 = asyncio.create_task(
        say_after(1, 'hello'))

    task2 = asyncio.create_task(
        say_after(2, 'world'))

    task3 = asyncio.create_task(
        say_after(0.5, 'Hai')
    )

    print(f"started at {time.strftime('%X')}")

    # Wait until both tasks are completed (should take
    # around 2 seconds.)
    await task1
    # await task2

    await asyncio.sleep(2)

    print(f"finished at {time.strftime('%X')}")


if __name__ == '__main__':
    asyncio.run(main())

started at 11:56:07
[1691380567.491296]: starting hello
[1691380567.491312]: starting world
[1691380567.491318]: starting Hai
[1691380567.992693]: ending Hai
[1691380568.4926028]: ending hello
[1691380569.492554]: ending world
finished at 11:56:10

应该把这里的 create_task, await 比作 socket 中的 write 和 flush 操作来理解，或者写日志中的 write 和 flush 操作。