How to avoid displaying errors caused after running subprocess.call

Question

So when I run subprocess.call in python, after running the script, if there are error messages caused by the bash, I would like to not display it to the user.
So for instance,

for i in range(len(official_links)):
    if(subprocess.call('pacman ' + '-Qi ' + official_links[i].replace('https://www.archlinux.org/packages/?q=', ''),shell=True, stdout=subprocess.PIPE) == 0):
        print(official_links[i].replace('https://www.archlinux.org/packages/?q=', '') + ' installed')
    else:
        print(official_links[i].replace('https://www.archlinux.org/packages/?q=', '') + ' not installed')

the command pacman -Qi packagename cheks if the packagename is already installed or not. When I run my script, if it is installed, I get no extra messages from the bash, only what I print. But if the package does not exist and an error is caused, both the error and my print gets printed on the screen.

Is there a way to avoid printing command errors too?

Thanks.

Matthieu Brucher · Accepted Answer · 2018-11-13 10:09:36Z

2

Redirect the stderr as well:

if(subprocess.call('pacman ' + '-Qi ' + official_links[i].replace('https://www.archlinux.org/packages/?q=', ''),shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE) == 0):

That's where the error is displayed.

answered Nov 13, 2018 at 10:09

Matthieu Brucher

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1 Comment

Huzo Over a year ago

That did the job! As a bonus question, may I ask if using this technique to avoid messages is prone to any specific problems? Thanks

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