title: Python - Implement iteration over certain class attributes on given order
body: <p>I have a <code>Position</code> class, and it has two attributes, <code>Lat</code> and <code>Lon</code>.</p>
  
  <p>I would like the following API by implementing <code>iterator</code> protocol (but some googling just confused me more):</p>
  
  <pre><code>pos = Position(30, 50)
  print pos.Latitude
  &gt; 30
  
  print pos.Longitude
  &gt; 50
  
  for coord in pos:
      print coord
  &gt; 30
  &gt; 50
  
  print list(pos)
  &gt; [30, 50]
  </code></pre>