Python: How to execute an external program

Question

How do I execute a program from within my program without blocking until the executed program finishes?

I have tried:

os.system()

But it stops my program till the executed program is stopped/closed. Is there a way to allow my program to keep running after the execution of the external program?

Answer 1

Consider using the subprocess module.

• Python 2: http://docs.python.org/2/library/subprocess.html
• Python 3: http://docs.python.org/3/library/subprocess.html

subprocess spawns a new process in which your external application is run. Your application continues execution while the other application runs.

• Ignacio Vazquez-Abrams: Unless you explicitly wait for it.
• Nick Bastin: os.system spawns a new process as well - subprocess just gives you more control over it.

Answer 2

You want subprocess.

Answer 3

You could use the subprocess module, but the os.system will also work. It works through a shell, so you just have to put an '&' at the end of your string. Just like in an interactive shell, it will then run in the background.

If you need to get some kind of output from it, however, you will most likely want to use the subprocess module.

Answer 4

You can use subprocess for that:

import subprocess
import codecs
# start 'yourexecutable' with some parameters
# and throw the output away
with codecs.open(os.devnull, 'wb', encoding='utf8') as devnull:
 subprocess.check_call(["yourexecutable",
 "-param",
 "value"],
 stdout=devnull, stderr=subprocess.STDOUT
 )