Python error raise NotImplementedError when trying to call shell command async

Question

I am new with Python programming. I want to call a few shell commands in parallel and get their result accumulated in a single array just like javascript promise.all() method.
I have the following code in Python

import asyncio
import os


commands = [
    'netstat -n | findstr 55601',
    'dir | findstr portMonitoring.py',
    'ssh 10.6.100.192 netstat'
]

async def job(cmd):
    # await asyncio.sleep(1)
    # return "HEE"
    # return os.popen(cmd).read()
    process = await asyncio.create_subprocess_exec(
        cmd, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE
    )

    return await process.communicate()



async def main():
    jobs = [job(cmd) for cmd in commands]
    done, pending = await asyncio.wait(jobs, return_when=asyncio.FIRST_COMPLETED)
    folders = []
    [folders.append(d.result()) for d in done]
    print("RESULT:", folders)

asyncio.run(main())

I am getting the following error and not able to find any solution, please assist Thanks.

Traceback (most recent call last):
  File "test.py", line 16, in job
    cmd, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE
  File "C:\DEV\Python3.7.4\lib\asyncio\subprocess.py", line 217, in create_subprocess_exec
    stderr=stderr, **kwds)
  File "C:\DEV\Python3.7.4\lib\asyncio\base_events.py", line 1529, in subprocess_exec
    bufsize, **kwargs)
  File "C:\DEV\Python3.7.4\lib\asyncio\base_events.py", line 458, in _make_subprocess_transport
    raise NotImplementedError
NotImplementedError

Answer 1

https://github.com/python/cpython/blob/master/Lib/asyncio/base_events.py#L493

It's a planned feature but it is not implemented yet. It will work in the future but the current versions don't support it.

I looked through the other branches and none of them are implemented. The subprocess module ( https://docs.python.org/3/library/subprocess.html ) is widely known and the asyncio support for it is not yet finished. The endpoints were defined but they are as of now not usable.

Answer 2

It is explained in the docs:

Python 3.7

https://docs.python.org/3.7/library/asyncio-platforms.html#asyncio-windows-subprocess

SelectorEventLoop on Windows does not support subproceses. On Windows, ProactorEventLoop should be used instead:

import asyncio

asyncio.set_event_loop_policy(
    asyncio.WindowsProactorEventLoopPolicy())

asyncio.run(your_code())

Python 3.8

The default event loop on Windows is now the ProactorEventLoop.