title: pandas dataframe groupby on multiindex
body: <p>I am using Pandas dataframe to read excel file and do some operation on that. I have a header with multiple rows, and now I want to group by a few column values. However I am not able to find the solution for this.</p>
  <p>Sample Excel:</p>
  <pre><code>    name                     address         contact_info   
      first_name  last_name   street  city    mobile  email
  1   AAA         BBB         XXX     YYY     102020  aaa@xyz.com
  2   111         222         333     444     239393  bbb@xyz.com
  3   BBB         333         XXX     dddd    102020  aaa@xyz.com
  </code></pre>
  <p>I want to group by street name and find values from other columns
  I tried this but it's not able to find street as it's multiindex.</p>
  <pre><code>df = pd.read_excel(&quot;test.xlsx&quot;, header=[0, 1], sheet_name=&quot;Sheet1&quot;)
  print df.groupby(&quot;street&quot;, level=-1)[[&quot;first_name&quot;, &quot;last_name&quot;, &quot;email&quot;]].apply(list)
  </code></pre>