Why coroutines cannot be used with run_in_executor?

Question

I want to run a service that requests urls using coroutines and multithread. However I cannot pass coroutines to the workers in the executor. See the code below for a minimal ex

Answer 1

You have to create and set a new event loop in the thread context in order to run coroutines:

import asyncio
from concurrent.futures import ThreadPoolExecutor


def run(corofn, *args):
    loop = asyncio.new_event_loop()
    try:
        coro = corofn(*args)
        asyncio.set_event_loop(loop)
        return loop.run_until_complete(coro)
    finally:
        loop.close()


async def main():
    loop = asyncio.get_event_loop()
    executor = ThreadPoolExecutor(max_workers=5)
    futures = [
        loop.run_in_executor(executor, run, asyncio.sleep, 1, x)
        for x in range(10)]
    print(await asyncio.gather(*futures))
    # Prints: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]


if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())