473,396 Members | 1,772 Online
Bytes | Software Development & Data Engineering Community
Post Job

Home Posts Topics Members FAQ

Join Bytes to post your question to a community of 473,396 software developers and data experts.

Interprocess communication

Hi Python Gurus,

I am writing a GUI app (on linux) using pygtk which would launch some
external applications and display their stdout and stderr inside the
output window of my application synchronously. I am using the
subprocess module's Popen to launch the external programs and to
capture their stdout and stderr. The problem is that, for some
external programs that I launch inside my interface, I am not able to
capture and display the stdout as the program *runs*.

After some investigation, I found out that this problem had nothing to
do with my GUI app not getting refreshed and I was able to reproduce
this problem with normal python scripts. Here is one such script

#File test.py
from subprocess import Popen
from subprocess import PIPE
import sys
if __name__ == '__main__':
prog = sys.argv[1]
proc = Popen(prog, shell = True, stdout = PIPE, bufsize = 0)
out = proc.stdout
while proc.poll() is None:
print out.readline()

Run this program as follows
$ test.py "ping -c 10 www.google.com"

Now, you would see the responses as if you just launched ping on the
command line. Now, lets look at another program. Here is a simple C++
program that prints numbers 1 to 10 at the passage of every second
(sort of a stopwatch)

#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
main ( )
{
timeval t1, t2;
gettimeofday(&t1, NULL);
int prev = -1;
int cur = 0;
while (true)
{
gettimeofday(&t2,NULL);
if(t2.tv_sec - t1.tv_sec 10)
break;
else
{
cur = t2.tv_sec-t1.tv_sec;
if (cur != prev)
{
printf("%d\r\n",cur);
prev = cur;
}
}
}
}

if you would build this program and call it lets say timer ($ g++ -o
timer timer.cpp) and run it with our python script like this

$python test.py "./timer"

you would see that every time you run the program your results vary
and on top of this the stdout of the timer program gets displayed all
at once presumably when the timer program has completed execution.

Why this discrepancy between the ping and timer programs? Is my
test.py script correct? Is there a better or a preferred method for
doing interprocess communication in Python.

Thanks!
Murali.

Jul 19 '07 #1
0 1472

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

2
by: Jeroen | last post by:
Question, We are in the process of creating a windows service in C#. Another GUI application, also written in C# has to communicate from another machine to this service. What is the best...
7
by: Daniel | last post by:
I search for a good way to communicate between processes. I have a main application(might be more instances) and an tool that should exchange information such as which user is logged in into the...
4
by: Charles Packer | last post by:
I need to do the following simple interprocess communication (IPC) among these processes that are all on the same box: -- A daemon waits for "I'm here" announcements from multiple clients -- One...
5
by: guy | last post by:
In the past I've used sockets in C++ to allow apps to communicate with each other over a local network. Is there anything better/more advanced in .NET or should I continue to use sockets and the...
3
by: James Aguilar | last post by:
Oh wise readers of comp.lang.python, Lend a newbie your ears. I have read several old articles from this group about memory mapping and interprocess communication and have Googled the sh** out...
7
by: Michael Butscher | last post by:
Hi, this is not really Python-specific but I need it for Python. I'm wanting a method for interprocess communication which is OS- independent (sockets would be the normal way to go), but which...
4
by: batista | last post by:
Hello all, I need suggestions and possibly solutions to the problem stated below: I have an application written purely in .NET ( Windows Form Application) and another application that is...
2
by: Murali | last post by:
Hi Python Gurus, I am writing a GUI app (on linux) using pygtk which would launch some external applications and display their stdout and stderr inside the output window of my application...
3
by: madankarmukta | last post by:
Hi all, I am very new to Implementation of the Interprocess communication.I am trying to implement the concept in c++.I created the pipe using Createnamedpipe() function ,connecting to that pipe...
0
by: Charles Arthur | last post by:
How do i turn on java script on a villaon, callus and itel keypad mobile phone
0
by: emmanuelkatto | last post by:
Hi All, I am Emmanuel katto from Uganda. I want to ask what challenges you've faced while migrating a website to cloud. Please let me know. Thanks! Emmanuel
1
by: Sonnysonu | last post by:
This is the data of csv file 1 2 3 1 2 3 1 2 3 1 2 3 2 3 2 3 3 the lengths should be different i have to store the data by column-wise with in the specific length. suppose the i have to...
0
by: Hystou | last post by:
There are some requirements for setting up RAID: 1. The motherboard and BIOS support RAID configuration. 2. The motherboard has 2 or more available SATA protocol SSD/HDD slots (including MSATA, M.2...
0
by: Hystou | last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can...
0
jinu1996
by: jinu1996 | last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven...
0
by: Hystou | last post by:
Overview: Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows...
0
tracyyun
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each...
0
agi2029
by: agi2029 | last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing,...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.