The most proper way to stop event loop after asyncio.run has been called?

Question

Considering the following code:

import asyncio


async def main() -> None:
    await asyncio.sleep(2**256)


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

What is the most proper way to terminate coroutine main, after it has been called by asyncio.run? When I invoked script and pressed CTRL + C, I saw an ugly traceback.

As I can see from the source code, asyncio.run does a lot of machinery behind the scenes, so I would like to continue using it.

Can you please clarify what exactly you need? asyncio.run already terminates the event loop. What "ugly traceback" did you see? — MisterMiyagi, Apr 13 '22 at 17:28
MisterMiyagi, I would not like to see the whole traceback message after I pressed CTRL + C, instread, say, I would like to see nothing (or an empty string). I do not think that writing custom signal handler is a good idea, since it would just duplicate asyncio.run logic. — John Shallow, Apr 13 '22 at 17:32
I do not think that calling loop.close is a good idea, since I have a pending task, which was initialized by asyncio.run. — John Shallow, Apr 13 '22 at 17:57
@JohnShallow so you want to run the task in background? Just you're asking how to stop event loop after `asyncio.run` is called. — Artyom Vancyan, Apr 14 '22 at 04:45

score -1 · Answer 1 · answered Apr 13 '22 at 17:58

You probably should handle the SIGINT signal.

import asyncio
import functools
import signal

async def main() -> None:
    await asyncio.sleep(2**256)

def handler(loop):
    ...


if __name__ == "__main__":
    loop = asyncio.get_event_loop()
    loop.add_signal_handler(signal.SIGINT, functools.partial(handler, loop=loop))
    loop.run_until_complete(main())

The question is how the handler should look like? If you want just close program without exception, use sys.exit()

def handler(loop):
    sys.exit()

However to close everything gracefully, you need to finish every task and stop the loop. See this topic for more insight.

The most proper way to stop event loop after asyncio.run has been called?

1 Answers1