Multiple stdin.write usage with python

Question

I have an Visual studio application which takes interactive arguments like

- PATH

On input , MENU #1 is displayed (which again accepts arguments/user input) and again on input , MENU #2 is displayed.

I need to call this VS application (exe) from Python . I have limitation to stick to Python 2.5 version.

I tried using subprocess.popen and stdin.write.

I am able to parse through MENU#1 but unable to proceed further to MENU #2 and so on...

Any hints/examples on achieving the above.?

My code looks like:

p = subprocess.Popen('app.exe',stdin=subprocess.PIPE,stdout=subprocess.PIPE,stderr=None)
p.stdin.write(file_path)  # for menu 1

time.sleep(0.5)

p.stdin.write('0')         # for menu 2..

...

o,e = p.communicate()

Are you sure that the exe reads from stdin and not directly from console? — Janne Karila
– Janne Karila, Commented Aug 23, 2012 at 8:50
Not very sure. Janne. I pressume that the exe reads from stdin (becoz, if in case i remove p.stdin.write('0') the behavior observed is as expected.) — Hemanth Deshpande
– Hemanth Deshpande, Commented Aug 23, 2012 at 10:01

Martijn Pieters · Accepted Answer · 2012-08-23 08:55:33Z

1

Use the pexpect module instead; it'll let you control a program with interactive input much better than the subprocess module can.

import pexpect

p = pexpect.spawn('app.exe')
p.sendline(file_path)
p.expect('Menu #2:.*')
p.sendline('0')

For windows, you can use wexpect.py instead, a port of the pexpect module to the Windows console.

edited Aug 23, 2012 at 8:55

answered Aug 23, 2012 at 8:43

Martijn Pieters

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4 Comments

Hemanth Deshpande Over a year ago

Dear Martijn, Many thanks for the advice. But i pressume that the pexpect module is for Linux environment. Currently i have setup running in Windows 7 / XP environment.

Martijn Pieters Over a year ago

Have you tried it? It's a pure-python module, so there won't be any compilation issues.

Hemanth Deshpande Over a year ago

Dear Martijn, Yes i tried it.>>> import pexpect Traceback (most recent call last): File "<stdin>", line 1, in <module> File "D:\Python25\Lib\site-packages\pexpect.py", line 85, in <module> support it. Pexpect is intended for UNIX-like operating systems.""") ImportError: No module named resource A critical module was not found. Probably this operating system does not support it. Pexpect is intended for UNIX-like operating systems. >>>

Martijn Pieters Over a year ago

Ah, the documentation states it'll work in a Cygwin environment, not on just Windows. Sorry about that.

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