title: list to dictionary conversion with multiple values per key?
body: <p>I have a Python list which holds pairs of key/value:</p>
  
  <pre><code>l = [[1, 'A'], [1, 'B'], [2, 'C']]
  </code></pre>
  
  <p>I want to convert the list into a dictionary, where multiple values per key would be aggregated into a tuple:</p>
  
  <pre><code>{1: ('A', 'B'), 2: ('C',)}
  </code></pre>
  
  <p>The iterative solution is trivial:</p>
  
  <pre><code>l = [[1, 'A'], [1, 'B'], [2, 'C']]
  d = {}
  for pair in l:
      if pair[0] in d:
          d[pair[0]] = d[pair[0]] + tuple(pair[1])
      else:
          d[pair[0]] = tuple(pair[1])
  
  print(d)
  
  {1: ('A', 'B'), 2: ('C',)}
  </code></pre>
  
  <p>Is there a more elegant, Pythonic solution for this task?</p>