Aggregate (SUM) by spark-sql

I am facing an issue while running aggregate of the order item subtotal by running in HiveContext. I am getting the result in below query

totalrevenue = sqlcontext.sql(“select sum(float(order_item_subtotal)) from order_items”)
But i am not able to verify the result of totalrevenue . when i try to print it gives me

DataFrame[_c0: double]

Can anyone please advise how to verify the result and is this enough to be able to get the answer in certification or we need to perform any other step?