title: Converting a Tuples List into a nested List using Python
body: <p>I want to convert a tuples list into a nested list using Python. How do I do that?</p>
  
  <p>I have a sorted list of tuples (sorted by the second value):</p>
  
  <pre><code>[(1, 5),  (5, 4), (13, 3), (4, 3), (3, 2), (14, 1), (12, 1), 
   (10, 1), (9, 1), (8, 1),  (7, 1), (6, 1), (2, 1)]
  </code></pre>
  
  <p>Now I want it to have like this (second value ignored and nested in lists):</p>
  
  <pre><code>[ [1], [5], [13, 4], [3], [14, 12, 10, 9, 8, 7, 6, 2] ]
  </code></pre>
  
  <p>I've seen other threads in here with <code>map</code> used for such things, but I don't completely understand it. Can anyone provide insight as to the 'correct' python way of doing this?</p>