Running an interactive command from within Python

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If you are communicating with a program that subprocess spawns, you should check out A non-blocking read on a subprocess.PIPE in Python. I had a similar problem with my application and found using queues to be the best way to do ongoing communication with a subprocess.

As for getting values from the user, you can always use the raw_input() builtin to get responses, and for passwords, try using the getpass module to get non-echoing passwords from your user. You can then parse those responses and write them to your subprocess’ stdin.

I ended up doing something akin to the following:

import sys
import subprocess
from threading import Thread

try:
    from Queue import Queue, Empty
except ImportError:
    from queue import Queue, Empty  # Python 3.x


def enqueue_output(out, queue):
    for line in iter(out.readline, b''):
        queue.put(line)
    out.close()


def getOutput(outQueue):
    outStr=""
    try:
        while True: # Adds output from the Queue until it is empty
            outStr+=outQueue.get_nowait()

    except Empty:
        return outStr

p = subprocess.Popen("cmd", stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=False, universal_newlines=True)

outQueue = Queue()
errQueue = Queue()

outThread = Thread(target=enqueue_output, args=(p.stdout, outQueue))
errThread = Thread(target=enqueue_output, args=(p.stderr, errQueue))

outThread.daemon = True
errThread.daemon = True

outThread.start()
errThread.start()

try:
    someInput = raw_input("Input: ")
except NameError:
    someInput = input("Input: ")

p.stdin.write(someInput)
errors = getOutput(errQueue)
output = getOutput(outQueue)

Once you have the queues made and the threads started, you can loop through getting input from the user, getting errors and output from the process, and processing and displaying them to the user.

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