Python Subprocess module

Dave Sampson samper.d at gmail.com
Fri Jul 13 23:15:49 CEST 2007


hey folks,

A simple question hopefully. despite all my searching I have not found a 
satisfactory response.

The goal. Interact with a command line program. Simple enough, but the 
key is INTERACT.

I tried the shell and comand approaches but that initiates, it does not 
allow interaction with the programs.

So then I went with Popen and such... which then led to the subprocess 
module.

I can create the object and read a few lines of output. but if I go too 
far then the program hangs. the number of lines will differ depandening 
on many function including the format of an input file so I can;t 
hardcode how many lines to read.

I want to read all of STDOUT without failing because I went out of range.

next I want to read the final line of the output because it tells me 
what is required for the next line of input.

I am supposed to be able to entre 'y' and return for the program to 
continue if I agree with what I see in the stdout.

A problem exists though that I have tried
'y'
'y\n'
'y\r'

and nothing seems to get the program going again for I still cant; read 
past the same point in the standard output. then I have to kill and 
start over.

So the next approach included looking at Pexpect, which got realy 
confusing realy fast and despite running fedora core and python 2.4.4 I 
would like my application to be cross platform and there is no Pexpect 
for Windows That I can see.

I have checked  out many mailing lists and posts and tutorials but they 
all admit to not be samples of complex interactivity. I guess I am 
having that special case.

ASPN Python cookbok provided some code for a new Popen Class that allows 
for interaction but I don't think I need to go that root....

I am essentialy trying to build and Python wrapper for a coomand line 
program that i want to build a GUI around.

Any links or suggestions would be great. Unfortunaetly I don't 
understand that abstract concepts in the manual reference. I am fresh in 
the python world and find examples better than technical abstracts.

Cheers



More information about the Python-list mailing list