title: How do you use subprocess.check_output() in Python?
body: <p>I have found documentation about subprocess.check_output() but I cannot find one with  arguments and the documentation is not very in depth. I am using Python 3 (but am trying to run a Python 2 file through Python 3)</p>
  
  <p>I am trying to run this command:
  <code>python py2.py -i test.txt</code></p>
  
  <p>-i is a positional argument for argparse, test.txt is what the -i is, py2.py is the file to run</p>
  
  <p>I have tried a lot of (non working) variations including:
  <code>py2output = subprocess.check_output([str('python py2.py '),'-i', 'test.txt'])</code></p>
  
  <p><code>py2output = subprocess.check_output([str('python'),'py2.py','-i', test.txt'])</code></p>