running executable from python with keyboard input

Question

I am calling a command line executable from python:

import subprocess
import os

def genParFiles(program):
    Path = "C:/00Working/99CygwinBin/"

    def exe_call(program):
        fullPath = Path + program
        subprocess.call(fullPath)

    exe_call(program)


if __name__=='__main__':
    main()

This works fine. The exe runs in the interpreter window.

Now, the program that I'm calling is waiting for me to press enter to start calculating, which I can do in the interpreter window with no problem.

My question is, how can I automate the 'enter' so I don't have to press it manually?

check out the docs for subprocess.call - you can provide an argument for stdin and presumably pass input through that? — thekaveman
– thekaveman, Commented Feb 1, 2014 at 0:19
@kaveman Ok... So what would I pass? I tried subprocess.call(fullPath, stdin=" ") but that did not work. — Flux Capacitor
– Flux Capacitor, Commented Feb 1, 2014 at 0:34
did you read the docs, at that link? stdin...Valid values are PIPE, an existing file descriptor (a positive integer), an existing file object, and None — thekaveman
– thekaveman, Commented Feb 1, 2014 at 0:45

dg99 · Accepted Answer · 2014-02-03 21:55:50Z

1

It's fairly straightforward with Popen:

p = subprocess.Popen(fullPath, shell=True, stdin=subprocess.PIPE)
stdO, stdE = p.communicate("foo\n")

::edit:: Fixed communicate call as pointed out in comments.

edited Feb 3, 2014 at 21:55

answered Feb 1, 2014 at 1:03

dg99

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4 Comments

Dane White Over a year ago

If you're using Python 3, then you will want to remove shell=True and add universal_newlines=True

Flux Capacitor Over a year ago

@dg99 Thanks for the help. I am using Python 3. The first line works and is calling the program. But I am getting an error with the 2nd line. "If self._communication_started and input: AttributeError: 'str' object has no attribute '_communication_started'" Any guidance you can give would be appreciated!

Flux Capacitor Over a year ago

@dg99 also, that second line should be subprocess.Popen.communicate right?

Flux Capacitor Over a year ago

@dg99 Nevermind, I got it. I made the 2nd line say: "stdO = p.communicate("foo\n") and that worked. Thanks for the tip.

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