title: How to extract any subset of digits from a numeric column
body: <p>I have an integer column(int64) in a dataframe with values as 20170811. (yyyymmdd)
  Now i need to extract 08 only and store it as a new column.</p>
  
  <pre><code>df['key'].floordiv(10000) 
  </code></pre>
  
  <p>gives me 2017. But i wanted 08 - how to get it ?</p>