title: Python; how to properly call another python script as a subprocess
body: <p>I know a very similar question has already been asked but since none of the solutions posted <a href="https://stackoverflow.com/questions/25752837/input-variable-into-python-call-subprocess">there</a> worked for my problem I try to make it replicable:</p>
  
  <p>So I'm calling <a href="http://gistncase.blogspot.co.at/2012/05/python-shapefile-merger-utility.html" rel="nofollow noreferrer">this script to merge some shapefiles</a> (all files in one folder) like this:</p>
  
  <pre><code>shpfiles = 'shapefile_a.shp shapefile_b.shp'
  subprocess.call(['python', 'shapemerger.py', '%s' % shpfiles])
  </code></pre>
  
  <p>I only get the Usage Instructions from the script so I cant determine what goes wrong. If i call the script directly in the terminal it works.
  Any help is appreciated.</p>