title: What's the cleanest (most Pythonic) way of creating a dictionary with list values from a sequence?
body: <p>I have a collection that looks like this:</p>
  
  <pre><code>stuff = [('key1', 1), ('key2', 2), ('key3', 3), 
           ('key1', 11), ('key2', 22), ('key3', 33),
           ('key1', 111), ('key2', 222), ('key3', 333),
           ]
  # Note: values aren't actually that nice. That would make this easy.
  </code></pre>
  
  <p>I want to turn it into a dictionary that looks like this:</p>
  
  <pre><code>dict_stuff = {'key1': [1, 11, 111],
                'key2': [2, 22, 222],
                'key3': [3, 33, 333],
                }
  </code></pre>
  
  <p>What's the nicest way to convert this data? The first method that comes to mind is:</p>
  
  <pre><code>dict_stuff = {}
  for k,v in stuff:
      dict[k] = dict.get(k, [])
      dict[k].append(v)
  </code></pre>
  
  <p>Is that the cleanest way to do this?</p>