Using Subprocess to Check sudo-apt install Return Value?

Question

I'm currently writing a shell script using Python 2.7. To install virtual-env I am using the following:

def setup_virtal_env(package): 
    try: 
        subprocess.call('apt-get update', shell=True)
        command = subprocess.call("apt-get install python-" + package, shell=True)
        proc = subprocess.check_call(str(command), stdin=PIPE, stderr=subprocess.STDOUT)
        stdoutdata, stderrdata = proc.communicate(),
        assert proc.returncode == 0, 'Installed failed...'
        print proc.returncode
    except subprocess.CalledProcessError: 
        print >> sys.stderr, "Execution failed", 'OSError,', 'trying pip...'
        'Installed virtualenv with pip...' if install_pip(package) else 'Pip failed...'

My question is how can I use subprocess.check_call or subprocess.check_output to check if the user already has virtualenv installed or if it installed correctly. As of right now when I call .check_call() it returns:

File "install_.py", line 121, in setup_virtal_env
proc = subprocess.check_call(str(command), stdin=PIPE, stderr=subprocess.STDOUT)
File "/usr/lib/python2.7/subprocess.py", line 535, in check_call
retcode = call(*popenargs, **kwargs)
File "/usr/lib/python2.7/subprocess.py", line 522, in call
return Popen(*popenargs, **kwargs).wait()
File "/usr/lib/python2.7/subprocess.py", line 710, in __init__
errread, errwrite)
File "/usr/lib/python2.7/subprocess.py", line 1327, in _execute_child
raise child_exception
OSError: [Errno 2] No such file or directory

Is there a way I can use subprocess to check if virtualenv is installed correctly?

Answer 1

When you want to use a command with arguments, you need to pass an array of args, like

suprocess.check_call(["apt-get","install", ...], ...)

Otherwise, the system will try to find an executable literally named "apt-get update", because spaces are legal filename characters. Of course it will then fail, giving you that error.

If you want to use a single string for your command, remember to use the shell=True argument

suprocess.check_call("apt-get install", shell=True, ...)