Asyncio + Multiprocessing + Unix

I have a pet project with the following logic: import asyncio, multiprocessing async def sub_main(): print('Hello from subprocess') def sub_loop(): asyncio.get_event_loop

Solution 1:

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 asyncio
from concurrent.futures import ProcessPoolExecutor

async 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))

Solution 2:

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, multiprocessing

async 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())