How to hide output of subprocess

For python >= 3.3, Redirect the output to DEVNULL:

import os
import subprocess

retcode = subprocess.call(['echo', 'foo'], 
    stdout=subprocess.DEVNULL,
    stderr=subprocess.STDOUT)

For python <3.3, including 2.7 use:

FNULL = open(os.devnull, 'w')
retcode = subprocess.call(['echo', 'foo'], 
    stdout=FNULL, 
    stderr=subprocess.STDOUT)

It is effectively the same as running this shell command:

retcode = os.system("echo 'foo' &> /dev/null")

Here's a more portable version (just for fun, it is not necessary in your case):

#!/usr/bin/env python
# -*- coding: utf-8 -*-
from subprocess import Popen, PIPE, STDOUT

try:
    from subprocess import DEVNULL # py3k
except ImportError:
    import os
    DEVNULL = open(os.devnull, 'wb')

text = u"René Descartes"
p = Popen(['espeak', '-b', '1'], stdin=PIPE, stdout=DEVNULL, stderr=STDOUT)
p.communicate(text.encode('utf-8'))
assert p.returncode == 0 # use appropriate for your program error handling here

Use subprocess.check_output (new in python 2.7). It will captures stdout as the return value of the function, which both prevents it from being sent to standard out and makes it availalbe for you to use programmatically. Like subprocess.check_call, this raises an exception if the command fails, which is generally what you want from a control-flow perspective. Example:

import subprocess
try:
    output = subprocess.check_output(['espeak', text])
except subprocess.CalledProcessError:
    # Handle failed call

You can also suppress stderr with:

    output = subprocess.check_output(["espeak", text], stderr=subprocess.STDOUT)

For earlier than 2.7, use

import os
import subprocess
with open(os.devnull, 'w')  as FNULL:
    try:
        output = subprocess._check_call(['espeak', text], stdout=FNULL)
    except subprocess.CalledProcessError:
        # Handle failed call

Here, you can suppress stderr with

        output = subprocess._check_call(['espeak', text], stdout=FNULL, stderr=FNULL)

As of Python3 you no longer need to open devnull and can call subprocess.DEVNULL.

Your code would be updated as such:

import subprocess
text = 'Hello World.'
print(text)
subprocess.call(['espeak', text], stderr=subprocess.DEVNULL)