run asyncio event loop in another thread.

main.py

import asyncio
import threading


class AsyncioBackground(threading.Thread):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.loop = asyncio.new_event_loop()

    def run(self):
        self.loop.run_forever()

    def run_coro_threadsafe(self, coro):
        finished = threading.Event()
        fut = asyncio.run_coroutine_threadsafe(coro, loop=self.loop)
        fut.add_done_callback(lambda _: finished.set())
        finished.wait()
        return fut.result()

    def stop(self):
        self.loop.call_soon_threadsafe(self.loop.stop)


if __name__ == '__main__':
    from datetime import datetime
    t = AsyncioBackground()
    t.start()

    async def raise_error():
        await asyncio.sleep(1)
        raise ValueError()

    print(datetime.now())
    try:
        t.run_coro_threadsafe(raise_error())
        print(datetime.now())
    finally:
        t.stop()