title: Unique list of dicts based on keys
body: <p>I have a list of dics:</p>
  
  <pre><code>     data = {}
       data['key'] = pointer_key
       data['timestamp'] = timestamp
       data['action'] = action
       data['type'] = type
       data['id'] = id
  
       list = [data1, data2, data3, ... ]
  </code></pre>
  
  <p>How can I ensure that for each data item in the list, only one such element exists for each "key"?  If there are two keys as seen below, the most recent timestamp would win:</p>
  
  <pre><code>    list = [{'key':1,'timestamp':1234567890,'action':'like','type':'photo',id:245},
              {'key':2,'timestamp':2345678901,'action':'like','type':'photo',id:252},
              {'key':1,'timestamp':3456789012,'action':'like','type':'photo',id:212}]
  
      unique(list)
  
      list = [{'key':2,'timestamp':2345678901,'action':'like','type':'photo',id:252},
              {'key':1,'timestamp':3456789012,'action':'like','type':'photo',id:212}]
  </code></pre>
  
  <p>Thanks.</p>