How do I pass a user input variable inside subprocess_check_output?

I am a beginner trying to get a shell command from a user in Pyramid and pass it to subprocess.check_output["thisisthecommand"]

The variable is stored in myvar. Eg:myvar="echo helloworld" How to pass this variable inside my subprocess check_output?

I tried doing this subprocess.check_output[myvar] but it doesnt work. Pyramid throws the error 'AttributeError:NoneType object has no attribute' Please help.

Solution

As per the documentation (and the examples therein) you need to separate command and arguments in the list. e.g,

subprocess.check_output(['echo', 'hello'])

should work. There is a shell option which would allow you to write subprocess.check_output('echo hello', shell=True) but that is best left alone for security reasons.

If you use a variable myvar containing the command, you can use shlex.split() to produce a list suitable for passing to check_output():

import shlex, subprocess
myvar = 'echo hello'
args = shlex.split(myvar)
output = subprocess.check_output(args)
>>> args
['echo', 'hello']

Incidentally, Python functions are invoked using using (), not [] - the latter used for indexing a sequence or accessing a dictionary by key.