Tornado v.s. asyncio (Python 3.5+)

asyncio.py

#! /usr/bin/env python3

import asyncio
import contextlib


async def ping(ip):
    p = await asyncio.create_subprocess_exec('ping', '-c', '4', ip, stdout=asyncio.subprocess.PIPE)
    async for line in p.stdout:
        print(line)
    await p.wait()


async def main():
    await asyncio.wait([
        ping('8.8.8.8'),
        ping('8.8.4.4'),
    ])


if __name__ == '__main__':
    with contextlib.closing(asyncio.get_event_loop()) as main_loop:
        main_loop.run_until_complete(main())

tornado.py

#! /usr/bin/env python3

from tornado import gen, ioloop, process


async def ping(ip):
    p = process.Subprocess(['ping', '-c', '4', ip], stdout=process.Subprocess.STREAM)
    await p.stdout.read_until_close(streaming_callback=print)
    await p.wait_for_exit()


async def main():
    await gen.multi([
        ping('8.8.8.8'),
        ping('8.8.4.4'),
    ])


if __name__ == '__main__':
    main_loop = ioloop.IOLoop.instance()
    main_loop.run_sync(main)

I get the below error on 3.5.1. What am i missing?

C:\Ashish\Research\Python>python async_ping.py
Task exception was never retrieved
future: <Task finished coro=<ping() done, defined at async_ping.py:6> exception=
NotImplementedError()>
Traceback (most recent call last):
File "C:\Python35\lib\asyncio\tasks.py", line 239, in _step
result = coro.send(None)
File "async_ping.py", line 7, in ping
p = await asyncio.create_subprocess_exec('ping', '-c', '4', ip, stdout=async
io.subprocess.PIPE)
File "C:\Python35\lib\asyncio\subprocess.py", line 212, in create_subprocess_e
xec
stderr=stderr, *_kwds)
File "C:\Python35\lib\asyncio\base_events.py", line 1026, in subprocess_exec
bufsize, *_kwargs)
File "C:\Python35\lib\asyncio\coroutines.py", line 206, in coro
res = func(_args, *_kw)
File "C:\Python35\lib\asyncio\base_events.py", line 267, in _make_subprocess_t
ransport
raise NotImplementedError
NotImplementedError
Task exception was never retrieved
future: <Task finished coro=<ping() done, defined at async_ping.py:6> exception=
NotImplementedError()>
Traceback (most recent call last):
File "C:\Python35\lib\asyncio\tasks.py", line 239, in _step
result = coro.send(None)
File "async_ping.py", line 7, in ping
p = await asyncio.create_subprocess_exec('ping', '-c', '4', ip, stdout=async
io.subprocess.PIPE)
File "C:\Python35\lib\asyncio\subprocess.py", line 212, in create_subprocess_e
xec
stderr=stderr, *_kwds)
File "C:\Python35\lib\asyncio\base_events.py", line 1026, in subprocess_exec
bufsize, *_kwargs)
File "C:\Python35\lib\asyncio\coroutines.py", line 206, in coro
res = func(_args, *_kw)
File "C:\Python35\lib\asyncio\base_events.py", line 267, in _make_subprocess_t
ransport
raise NotImplementedError
NotImplementedError

I suspect that's a Windows specific problem, e.g. missing proper event loop implementation.
Sadly I don't have a Windows machine for Python developing, so I can't help. :(

Your example is so simple and clear that it helps me understand async programming in Python.
Thank you so much.

For working Windows asyncio you need to change EventLoop:
add:
loop = asyncio.ProactorEventLoop()
asyncio.set_event_loop(loop)

also "-c 4" for windows works not the same way as in Linux, so you just need to remove this arguments.