Is there a way to check if a subprocess is still running?

python subprocess
ahura picture ahura · Apr 7, 2017 · Viewed 65.9k times · Source

I'm launching a number of subprocesses with subprocess.Popen in Python. I'd like to check whether one such process has completed. I've found two ways of checking the status of a subprocess, but both seem to force the process to complete. One is using process.communicate() and printing the returncode, as explained here. Another is simply calling process.wait() and checking that it returns 0.

Is there a way to check if a process is still running without waiting for it to complete if it is?

Answer

stovfl picture stovfl · Apr 7, 2017

Ouestion: ... a way to check if a process is still running ...

You can do it for instance: 

p = subprocess.Popen(...
"""
A None value indicates that the process hasn't terminated yet.
"""
poll = p.poll()
if poll == None:
  # p.subprocess is alive

Python » 3.6.1 Documentation popen-objects

Tested with Python:3.4.2

Related questions

How to call an external command?

How do you call an external command (as if I'd typed it at the Unix shell or Windows command prompt) from within a Python script?

Read More
Running shell command and capturing the output

I want to write a function that will execute a shell command and return its output as a string, no matter, is it an error or success message. I just want to get the same result that I would have …

Read More
Store output of subprocess.Popen call in a string

I'm trying to make a system call in Python and store the output to a string that I can manipulate in the Python program. #!/usr/bin/python import subprocess p2 = subprocess.Popen("ntpq -p") I've tried a few things including …

Read More