title: How to run python script for QGIS from outside
body: <p>I have hundred shape files in a folder. I have following tasks</p>
  
  <ol>
  <li>Find out what are the fields in each shapefile</li>
  <li>If there is no field 'City' in any of the shapefiles I have to add that field in those shapefile.</li>
  </ol>
  
  <p>I can access each layer in python console in QGIS using
  iface.activeLayer()</p>
  
  <p>But I want to run a stand alone python script which will perform the tasks. Can anyone help?</p>