longrunning_external_processes.py

#!/usr/bin/env python3.5
# Adapted from J.F. Sebastian's answer at http://stackoverflow.com/a/34027086/340811
import asyncio
import sys
from asyncio.subprocess import PIPE, STDOUT

async def get_lines(shell_command):
    p = await asyncio.create_subprocess_shell(shell_command, stdin=PIPE, stdout=PIPE, stderr=STDOUT)
    return (await p.communicate())[0].splitlines()

async def main():
    # get commands output concurrently
    coros = [get_lines('sleep {i:d}; echo {i:d}'.format(i=i)) for i in reversed(range(1000))]
    for f in asyncio.as_completed(coros): # print in the order they finish
        print(await f)

if sys.platform.startswith('win'):
    loop = asyncio.ProactorEventLoop() # for subprocess' pipes on Windows
    asyncio.set_event_loop(loop)
else:
    loop = asyncio.get_event_loop()

loop.run_until_complete(main())
loop.close()