title: Can I merge 2 dataframes with 2 same column labels using pandas
body: <p>Here's my dataframes:</p>
  <pre><code>df1
  Campaign                               Ad Group            Sales
  AMZ CT BR Leather Shoes ABCDEFG1234   [leather shoes]      $10
  AMZ CT BR Leather Shoes ABCDEFG1234   &quot;leather shoes&quot;      $10
  AMZ CT NB Leather Shoes ABCDEFG1234   [leather shoes]      $20
  AMZ OG BR Bag HGIJK567                 bag                 $30
  AMZ OG NB Bag HGIJK567 Desktop         bag                 $40
  
  df2
  Campaign                              Ad Group             Spend        
  GA BR Leather Shoes ABCDEFG1234      [leather shoes]        $5      
  GA BR Leather Shoes ABCDEFG1234      &quot;leather shoes&quot;        $5
  GA NB Leather Shoes ABCDEFG1234      [leather shoes]        $6
  GA BR Bag HGIJK567                    bag                   $7
  GA NB Bag HGIJK567 Desktop            bag                   $8
  
  </code></pre>
  <p>Here's the result I like when I merge the 2 dataframes:</p>
  <pre><code>df3
  Campaign                             Ad Group          Spend   Sales
  CT BR Leather Shoes ABCDEFG1234     [leather shoes]     $5      $10
  CT BR Leather Shoes ABCDEFG1234     &quot;leather shoes&quot;     $5      $10    
  CT NB Leather Shoes ABCDEFG1234     [leather shoes]     $6      $20
  OG BR Bag HGIJK567                   bag                $7      $30
  OG NB Bag HGIJK567 Desktop           bag                $8      $40
  
  </code></pre>
  <p>I would like to combine the values of the campaigns and ad groups in the merged dataframe.</p>