title: Convert string column to integer
body: <p>I have a dataframe like below</p>
  
  <pre><code>    a   b
  0   1   26190
  1   5   python
  2   5   580
  </code></pre>
  
  <p>I want to make column <code>b</code> to host only integers, but as you can see <code>python</code> is not int convertible, so I want to delete the row at index <code>1</code>. My expected out put has to be like</p>
  
  <pre><code>    a   b
  0   1   26190
  1   5   580
  </code></pre>
  
  <p>How to filter and remove using pandas in python?</p>