Interacting with another command line program in Python.

Question

I need to write a Python script that can run another command line program and interact with it's stdin and stdout streams. Essentially, the Python script will read from the target command line program, intelligently respond by writing to its stdin, and then read the results from the program again. (It would do this repeatedly.)

I've looked through the subprocess module, and I can't seem to get it to do this read/write/read/write thing that I'm looking for. Is there something else I should be trying?

Answer 1

see the question http://stackoverflow.com/questions/989129/wxpython-how-to-create-a-bash-shell-window/1005079#1005079

there I have given a full fledged interaction with bash shell reading stdout and stderr and communicating via stdin

main part is extension of this code

bp = Popen('bash', shell=False, stdout=PIPE, stdin=PIPE, stderr=PIPE)
bp.stdin.write("ls\n")
bp.stdout.readline()

if we read all data it will get blocked so the link to script I have given does it in a thread. That is a complete wxpython app mimicking bash shell partially.

Answer 2

To perform such detailed interaction (when, outside of your control, the other program may be buffering its output unless it thinks it's talking to a terminal) needs something like pexpect -- which in turns requires pty, a Python standard library module that (on operating systems that allow it, such as Linux and Mac OS x) implements "pseudo-terminals".

Life is harder on Windows, but maybe this zipfile can help -- it's supposed to be a port of pexpect to Windows (sorry, I have no Windows machine to check it on). The project in question, called wexpect, lives here.