title: Pandas DataFrame adding column after groupby
body: <p>I have the following csv file: </p>
  
  <pre><code>type    sku quantity    country account
  Order   CHG-FOOD1COMP-CA    1   usa hch
  Order   CHG-FOOD2COMP-CA    1   usa hch
  Order   CHG-FOOD2COMP-CA    1   usa hch
  Order   CHG-FOOD1COMP-CA    1   usa hch
  Order   CHG-FOODCONT1-CA    1   usa hch
  Order           usa hch
  Order   Q7-QDH0-EBB5-CA 1   usa hch
  Order   CHG-FRY-12PT5-CA    1   usa hch
  Order   Q7-QDH0-EBB5-CA 1   usa hch
  Order   Q7-QDH0-EBB5-CA 1   usa hch
  Order   CHG-FRY-12PT5-CA    1   usa hch
  Order   CB-BB-CLR12-CA  1   usa hch
  Order   CB-BB-AMB12-CA  1   usa hch
  
  Order           usa hch
  Order   CB-BB-AMB12-CA  1   usa hch
  Order   CHG-FRY-12PT5-CA    1   usa hch
  Order   CB-BB-CLR12-CA  1   usa hch
  Order   CHG-FRY-12PT5-CA    1   usa hch
  Order   CHG-FOODCONT1-CA    1   usa hch
  Refund  CHG-FRY-9PT5-CA 1   usa hch
  Order   CHG-FOOD1COMP-CA    1   usa hch
  </code></pre>
  
  <p>I have the following data. I want to get the the total quantity per sku.</p>
  
  <pre><code>SQL: Select sku sum(quantity) As TotalQty,  country, account
       From (usa_chc_Date.csv)
       group by sku,...
  </code></pre>
  
  <p>I dont mind getting the sum first and then adding those country/account columns that are always the same.
  My purpose is to store the info in these csv so they are easy to load into django and then delete the files. 
  This is what I am looking for:  </p>
  
  <pre><code>sku   TotalQty country account
  sku1   7       mx     chc
  sku3   4       mx     chc
  sku4   2       mx     chc
  sku5   1       mx     chc
  sku6   7       mx     chc
  sku7   9       mx     chc
  </code></pre>
  
  <p>I also named the file to include the country/account info. I guess I could just use the file, and strip the country and account as I save the model.</p>
  
  <p>side note-the accounts do not change since they are on the same report. Once they are loaded they skus can have duplicates but they have different countries. </p>
  
  <p>I tried this:        </p>
  
  <pre><code> df = df.groupby(['sku','quantity']).sum()
  </code></pre>