Non-blocking read on a stream in python.

Posted by Mathieu Pagé on Stack Overflow See other posts from Stack Overflow or by Mathieu Pagé
Published on 2008-12-17T17:56:34Z Indexed on 2010/03/18 8:41 UTC
Read the original article Hit count: 807

Filed under:

python

|

subprocess

|

nonblocking

|

io

Hi,

I'm using the subprocess module to start a subprocess and connect to it's output stream (stdout). I want to be able to execute non-blocking reads on its stdout. Is there a way to make .readline non-bloking or to check if there is data on the stream before I invoke .readline? I'd like this to be portable or at least work under Windows and Linux.

here is how I do it for now (It's blocking on the .readline if no data is avaible):

p = subprocess.Popen('myprogram.exe', stdout = subprocess.PIPE)
str = p.stdout.readline()

Thanks for your help.

© Stack Overflow or respective owner

Related posts about python

unmet dependencies in Ubuntu 12.04

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I tried today to install a dvb-card on my Ubuntu 12.04 (Linux blauhai-linux 3.2.0-25-generic #40-Ubuntu SMP Wed May 23 20:30:51 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux ). The installation failed with an error. After that, i tried to install python (it was already installed but i got this error): linux:~$… >>> More
How can I get sikuli-ide to work?

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I installed sikuli-ide with sudo apt-get install sikuli-ide Everything was fine until I tried to start it from the terminal. I typed sikuli-ide But the only response I got was [info] locale: en_US The application was not started, furthermore there is no desktop file and sikuli-ide does not… >>> More
Getting PATH right for python after MacPorts install

as seen on Super User - Search for 'Super User'
I can't import some python libraries (PIL, psycopg2) that I just installed with MacPorts. I looked through these forums, and tried to adjust my PATH variable in $HOME/.bash_profile in order to fix this but it did not work. I added the location of PIL and psycopg2 to PATH. I know that Terminal is… >>> More
call python with system() in R to run a python script emulating the python console

as seen on Stack Overflow - Search for 'Stack Overflow'
I want to pass a chunk of Python code to Python in R with something like system('python ...'), and I'm wondering if there is an easy way to emulate the python console in this case. For example, suppose the code is "print 'hello world'", how can I get the output like this in R? >>> print… >>> More
Python - Calling a non python program from python?

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I am currently struggling to call a non python program from a python script. I have a ~1000 files that when passed through this C++ program will generate ~1000 outputs. Each output file must have a distinct name. The command I wish to run is of the form: program_name -input -output -o1 -o2… >>> More

Related posts about subprocess

Why doesn't Apache2::SubProcess spawn my subprocess?

as seen on Stack Overflow - Search for 'Stack Overflow'
The following script works without errors, but /tmp/test.touch is not being created (even being checked later in the command line). It seems to me as if $r->spawn_proc_prog doesn't spawn a process. What may cause the problem? #!/usr/bin/perl use strict; use warnings; use Apache2::RequestUtil; use… >>> More
subprocess.Popen doesn't work when args is sequence

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm having a problem with subprocess.Popen when args parameter is given as sequence. For example: import subprocess maildir = "/home/support/Maildir" This works (it prints the correct size of /home/support/Maildir dir): size = subprocess.Popen(["du -s -b " + maildir], shell=True, … >>> More
Properly using subprocess.PIPE in python?

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm trying to use subprocess.Popen to construct a sequence to grab the duration of a video file. I've been searching for 3 days, and can't find any reason online as to why this code isn't working, but it keeps giving me a blank result: import sys import os import subprocess def main(): the_file… >>> More
why does python.subprocess hang after proc.communicate()?

as seen on Stack Overflow - Search for 'Stack Overflow'
I've got an interactive program called my_own_exe. First, it prints out alive, then you input S\n and then it prints out alive again. Finally you input L\n. It does some processing and exits. However, when I call it from the following python script, the program seemed to hang after printing out the… >>> More
Unbuffered subprocess output (last line missing)

as seen on Stack Overflow - Search for 'Stack Overflow'
I must be overlooking something terribly obvious. I need to execute a C program, display its output in real time and finally parse its last line, which should be straightforward as the last line printed is always the same. process = subprocess.Popen(args, shell = True, … >>> More