title: Geodjango: PointField and GEOSGeometry
body: <p>If I can do this:</p>
  
  <pre><code>&gt;&gt;&gt; from django.contrib.gis.geos import GEOSGeometry
  &gt;&gt;&gt; from django.contrib.gis.geos import Point
  &gt;&gt;&gt; point = GEOSGeometry('POINT(1 5)')
  &gt;&gt;&gt; print point
  POINT (1.0000000000000000 5.0000000000000000)
  </code></pre>
  
  <p>Why can I not do this:</p>
  
  <pre><code>&gt;&gt;&gt; lat = 1
  &gt;&gt;&gt; lon = 5
  &gt;&gt;&gt; point = GEOSGeometry('POINT(lat lon)')
  
  GEOS_ERROR: ParseException: Expected number but encountered word: 'lat'
  GEOSException: Error encountered checking Geometry returned from GEOS C function "GEOSWKTReader_read_r".
  </code></pre>
  
  <p>How can I use a variable to create a GEOSGeometry object?</p>