title: Python-selecting specified items from dictionary list
body: <p>Let's say I have list of cars:</p>
  
  <pre><code>car=[{'model':'ferrari', 'color': 'red', 'price':1200},
  {'model':'lamborgini', 'color': 'blue', 'price':2000},
  {'model':'ferrari', 'color': 'yellow', 'price':1000},
  {'model':'ferrari', 'color': 'yellow', 'price':500}]
  </code></pre>
  
  <p>I want to select the cheapest car for every model-color combination(cheapest red lamborgini, cheapest green ferrari etc) and put them in new list.</p>
  
  <p>The output should be:</p>
  
  <pre><code>[{'model':'ferrari', 'color': 'red', 'price':1200},
  {'model':'lamborgini', 'color': 'blue', 'price':2000},
  {'model':'ferrari', 'color': 'yellow', 'price':500}]
  </code></pre>
  
  <p>How can I do this?</p>