Answer by Louis Maddox for Close asyncio loop on KeyboardInterrupt - Run stop routine

You want to add a signal handler as shown in this example in the docs:

import asyncioimport functoolsimport osimport signaldef ask_exit(signame, loop):    print("got signal %s: exit" % signame)    loop.stop()async def main():    loop = asyncio.get_running_loop()    for signame in {'SIGINT', 'SIGTERM'}:        loop.add_signal_handler(            getattr(signal, signame),            functools.partial(ask_exit, signame, loop))    await asyncio.sleep(3600)print("Event loop running for 1 hour, press Ctrl+C to interrupt.")print(f"pid {os.getpid()}: send SIGINT or SIGTERM to exit.")asyncio.run(main())

That's a bit of an overcomplicated/outdated example though, consider it more like this (your coroutine code goes where the asyncio.sleep call is):

import asynciofrom signal import SIGINT, SIGTERMasync def main():    loop = asyncio.get_running_loop()    for signal_enum in [SIGINT, SIGTERM]:        loop.add_signal_handler(signal_enum, loop.stop)    await asyncio.sleep(3600) # Your code hereasyncio.run(main())

At this point a Ctrl + C will break the loop and raise a RuntimeError, which you can catch by putting the asyncio.run call in a try/except block like so:

try:    asyncio.run(main())except RuntimeError as exc:    expected_msg = "Event loop stopped before Future completed."    if exc.args and exc.args[0] == expected_msg:        print("Bye")    else:        raise

That's not very satisfying though (what if something else caused the same error?), so I'd prefer to raise a distinct error. Also, if you're exiting on the command line, the proper thing to do is to return the proper exit code (in fact, the code in the example just uses the name, but it's actually an IntEnum with that numeric exit code in it!)

import asynciofrom functools import partialfrom signal import SIGINT, SIGTERMfrom sys import stderrclass SignalHaltError(SystemExit):    def __init__(self, signal_enum):        self.signal_enum = signal_enum        print(repr(self), file=stderr)        super().__init__(self.exit_code)    @property    def exit_code(self):        return self.signal_enum.value    def __repr__(self):        return f"\nExitted due to {self.signal_enum.name}"def immediate_exit(signal_enum, loop):    loop.stop()    raise SignalHaltError(signal_enum=signal_enum)async def main():    loop = asyncio.get_running_loop()    for signal_enum in [SIGINT, SIGTERM]:        exit_func = partial(immediate_exit, signal_enum=signal_enum, loop=loop)        loop.add_signal_handler(signal_enum, exit_func)    await asyncio.sleep(3600)print("Event loop running for 1 hour, press Ctrl+C to interrupt.")asyncio.run(main())

Which when Ctrl + C'd out of gives:

python cancelling_original.py

⇣

Event loop running for 1 hour, press Ctrl+C to interrupt.^CExitted due to SIGINT

echo $?

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2

Now there's some code I'd be happy to serve! :^)

P.S. here it is with type annotations:

from __future__ import annotationsimport asynciofrom asyncio.events import AbstractEventLoopfrom functools import partialfrom signal import Signals, SIGINT, SIGTERMfrom sys import stderrfrom typing import Coroutineclass SignalHaltError(SystemExit):    def __init__(self, signal_enum: Signals):        self.signal_enum = signal_enum        print(repr(self), file=stderr)        super().__init__(self.exit_code)    @property    def exit_code(self) -> int:        return self.signal_enum.value    def __repr__(self) -> str:        return f"\nExitted due to {self.signal_enum.name}"def immediate_exit(signal_enum: Signals, loop: AbstractEventLoop) -> None:    loop.stop()    raise SignalHaltError(signal_enum=signal_enum)async def main() -> Coroutine:    loop = asyncio.get_running_loop()    for signal_enum in [SIGINT, SIGTERM]:        exit_func = partial(immediate_exit, signal_enum=signal_enum, loop=loop)        loop.add_signal_handler(signal_enum, exit_func)    return await asyncio.sleep(3600)print("Event loop running for 1 hour, press Ctrl+C to interrupt.")asyncio.run(main())

The advantage of a custom exception here is that you can then catch it specifically, and avoid the traceback being dumped to the screen

try:    asyncio.run(main())except SignalHaltError as exc:    # log.debug(exc)    passelse:    raise