title: add a value to pre-existing dictionary key in python
body: <p>I've been trying to add a value to a pre-existing dictionary key. The value comes from the db.Model <code>Car</code> with the property named <code>price</code>.</p>
  
  <p>Tried two blocks of code (below) but have been getting the AttributeError: 'GqlQuery' object has no attribute 'price'.</p>
  
  <pre><code>items = {"BE1234":"2","BE1923":"3","BE2032":"1", etc}
  ------------------------------------------------------------
  block 1)
  for item in items:
    cars = db.GqlQuery('SELECT * FROM Car WHERE item=:1',item)
    items[item] = cars.price
  ------------------------------------------------------------
  block 2)
  for item in items:
    cars = db.GqlQuery('SELECT * FROM Car WHERE item=:1',item)
    items.update({item:cars.price})
  </code></pre>
  
  <p>What I'm looking to get is:</p>
  
  <p><code>items = {"BE1234":["2","100"],"BE1923":["31","200"],"BE2032":["19","300"], etc}</code></p>
  
  <p><strong>Update (final working code)</strong></p>
  
  <pre><code>for item in items:
    cars = db.GqlQuery('SELECT * FROM Car WHERE item=:1',item)
    for car in cars:
      items[item]=[items[item],str(car.price)]
  </code></pre>