How to hide output of subprocess in Python 2.7
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18-06-2021 - |
Вопрос
I'm using eSpeak on Ubuntu and have a Python 2.7 script that prints and speaks a message:
import subprocess
text = 'Hello World.'
print text
subprocess.call(['espeak', text])
eSpeak produces the desired sounds, but clutters the shell with some errors (ALSA lib..., no socket connect) so i cannot easily read what was printed earlier. Exit code is 0.
Unfortunately there is no documented option to turn off its verbosity, so I'm looking for a way to only visually silence it and keep the open shell clean for further interaction.
How can I do this?
Решение
Redirect the output to DEVNULL:
import os
import subprocess
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")
Update: This answer applies to the original question relating to python 2.7. As of python >= 3.3 an official subprocess.DEVNULL
symbol was added.
retcode = subprocess.call(['echo', 'foo'],
stdout=subprocess.DEVNULL,
stderr=subprocess.STDOUT)
Другие советы
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 suppress stdout and raise an exception if the command fails. (It actually returns the contents of stdout, so you can use that later in your program if you want.) Example:
import subprocess
try:
subprocess.check_output(['espeak', text])
except subprocess.CalledProcessError:
# Do something
You can also suppress stderr with:
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:
subprocess._check_call(['espeak', text], stdout=FNULL)
except subprocess.CalledProcessError:
# Do something
Here, you can suppress stderr with
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)
Why not use commands.getoutput() instead?
import commands
text = "Mario Balotelli"
output = 'espeak "%s"' % text
print text
a = commands.getoutput(output)