title: List comprehension list of lists
body: <p>I have a list of lists, and would like to use list comprehension to apply a function to each element in the list of lists, but when I do this, I end up with one long list rather than my list of lists.</p>
  
  <p>So, I have</p>
  
  <pre><code>x = [[1,2,3],[4,5,6],[7,8,9]]
  [number+1 for group in x for number in group]
  [2, 3, 4, 5, 6, 7, 8, 9, 10]
  </code></pre>
  
  <p>But I want to get</p>
  
  <pre><code>[[2, 3, 4], [5, 6, 7], [8, 9, 10]]
  </code></pre>
  
  <p>How do I go about doing this?</p>