Asyncio interactive subprocess communication, where subprocess is python script.

gistfile1.py

'''
test.py look like this::

    msg = 'prompt'
    for i in range(1, 4):
        msg = input(msg * i + '\n') 

'''
import sys
import asyncio

@asyncio.coroutine
def interactive_popen():
    proc = yield from asyncio.create_subprocess_exec(
        sys.executable, '-u', 'test.py', # python --help | grep '\-u'
        stdin=asyncio.subprocess.PIPE,
        stdout=asyncio.subprocess.PIPE)
    
    try:
        while True:
            print((yield from proc.stdout.readline()).decode())
            # note what sign of new line is required
            proc.stdin.write(b'test\n')
            drain = proc.stdin.drain()
            if drain is not ():
                yield from drain
    except ConnectionResetError:
        pass
        
    
if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(interactive_popen())