title: Pandas select n middle rows
body: <p>Suppose I have a dataframe, <strong>df</strong> like this</p>
  
  <pre><code>col1 col2 col3
   1     2     34
   11    32    32
   21    62    34
   31    12    31
   13    82    35
   11    32    33
   41    32    33
  </code></pre>
  
  <p>and I want to select 3 rows after first 2 rows, that is I want to select these rows</p>
  
  <pre><code> 21    62    34
   31    12    31
   13    82    35
  </code></pre>
  
  <p>How can I do this?</p>