title: subprocess.call does not wait for the process to complete
body: <p>Per Python documentation, <code>subprocess.call</code> should be blocking and wait for the subprocess to complete. In this code I am trying to convert few <code>xls</code> files to a new format by calling <code>Libreoffice</code> on command line. I assumed that the call to subprocess call is blocking but seems like I need to add an artificial delay after each call otherwise I miss few files in the <code>out</code> directory.</p>
  
  <p>what am I doing wrong? and why do I need the delay?</p>
  
  <pre><code>from subprocess import call
  
  for i in range(0,len(sorted_files)):
              args = ['libreoffice', '-headless', '-convert-to',
                      'xls', "%s/%s.xls" %(sorted_files[i]['filename'],sorted_files[i]['filename']), '-outdir', 'out']
              call(args)
              var = raw_input("Enter something: ") # if comment this line I dont get all the files in out directory
  </code></pre>
  
  <p><strong>EDIT</strong> It might be hard to find the answer through the comments below. I used <code>unoconv</code> for document conversion which is blocking and easy to work with from an script.</p>