title: How to slice column values in Python pandas DataFrame
body: <p>I have a dataframe like this- </p>
  
  <pre><code>element id  year    month   days    tmax    tmin
  0   MX17004 2010    1   d1          NaN      NaN
  1   MX17004 2010    1   d10         NaN      NaN
  2   MX17004 2010    1   d11         NaN      NaN
  3   MX17004 2010    1   d12         NaN      NaN
  4   MX17004 2010    1   d13         NaN      NaN
  </code></pre>
  
  <p>where I want to further break days column like this
  **</p>
  
  <pre><code>days
  1
  10
  11
  12
  13
  </code></pre>
  
  <p>**
  I have tried a couple of ways, but not successful in getting the output. Can someone please help or some clue?</p>