title: Refresh indices in Pandas Dataframe
body: <p>I have deleted some rows in a pandas DataFrame, but in the new DataFrame the indices are not refreshed, i.e.
  from this:</p>
  
  <pre><code>     id  marks
   1  123 45
   2  124 67
   3  127 89
   4  257 10
   5  345 34
  </code></pre>
  
  <p>I have obtained:</p>
  
  <pre><code>    id  marks
   2  124 67
   4  257 10
   5  345 34
  </code></pre>
  
  <p>While I want:</p>
  
  <pre><code>    id  marks
   1  124 67
   2  257 10
   3  345 34
  </code></pre>