title: Calling filter with a variable for field name
body: <p>Is there a way to call filter on a queryset where one of the fieldnames is a variable?</p>
  
  <p>For example I have something like:</p>
  
  <p><strong><code>models.py</code></strong></p>
  
  <pre><code>class Playlist(models.Model):
      video = ...
  </code></pre>
  
  <p><strong><code>views.py</code></strong></p>
  
  <pre><code>field_name = 'video'
  Playlist.objects.filter(field_name=v)
  </code></pre>
  
  <p>Which of course results in an error that <code>field_name</code> is not an attribute upon which <code>Playlist</code> can be filtered.</p>