title: How to transpose dataframe columns into rows in pandas
body: <p>I have below dataframe and want to transpose the columns aftr 3rd column into rows. Please help on this.</p>
  
  <pre><code>df:
  country year    perc    data1   data2   data3
  IN      2015    hjk     75      81      96
  US      2015    KTM     100     289     632
  
  Results:                
  country year    perc    TransposedColumn    Value   
  IN      2015    hjk     data1               75  
  IN      2015    hjk     data2               81  
  IN      2015    hjk     data3               96  
  US      2015    KTM     data1               100 
  US      2015    KTM     data2               289 
  US      2015    KTM     data3               632 
  </code></pre>