Suppress output from subprocess.Popen

Question

How do you stop the output from subprocess.Popen from being output? Printing can sometimes be slow if there is a great deal of it.

Answer 1

In Python 3.3+ you could use subprocess.DEVNULL, to suppress the output:

from subprocess import DEVNULL, STDOUT, check_call

check_call([cmd, arg1, arg2], stdout=DEVNULL, stderr=STDOUT)

Remove stderr=STDOUT if you don't want to suppress stderr also.

Answer 2

If you want to totally throw it away:

import subprocess
import os
with open(os.devnull, 'w') as fp:
    cmd = subprocess.Popen(("[command]",), stdout=fp)

If you are using Python 2.5, you will need from __future__ import with_statement, or just don't use with.