asyncio + multiprocessing + unix

First, you should consider using loop.run_in_executor with a ProcessPoolExecutor if you plan to run python subprocesses from within the loop. As for your problem, you can use the event loop policy functions to set a new loop:

import asynciofrom concurrent.futures import ProcessPoolExecutorasync def sub_main():    print('Hello from subprocess')def sub_loop():    loop = asyncio.new_event_loop()    asyncio.set_event_loop(loop)    loop.run_until_complete(sub_main())async def start(executor):    await asyncio.get_event_loop().run_in_executor(executor, sub_loop)if __name__ == '__main__':    executor = ProcessPoolExecutor()    asyncio.get_event_loop().run_until_complete(start(executor))

You should always add a check to see how you're running the code (the if __name__ == '__main__': part. Your subprocess is running everything in the module a 2nd time, giving you grief (couldn't resist).

import asyncio, multiprocessingasync def sub_main():    print('Hello from subprocess')def sub_loop():    asyncio.get_event_loop().run_until_complete(sub_main())async def start():    multiprocessing.Process(target=sub_loop).start()if __name__ == '__main__':    asyncio.get_event_loop().run_until_complete(start())