title: Pandas, merging two dataframes on multiple columns, and multiplying result
body: <p>I have a dataframe,df1 that looks something like this:</p>
  
  <pre><code>Name Event Factor1
  John A     2
  John B     3
  Ken  A     1.5
  ....
  </code></pre>
  
  <p>and an additional dataframe,df2 like this:</p>
  
  <pre><code>Name Event Factor2
  John A     1.2
  John B     .5
  Ken  A     2
  </code></pre>
  
  <p>I would like to join both of these dataframes on the two columns Name and Event, with the resulting columns factor 1 and 2 multiplied by each other.</p>
  
  <pre><code>Name Event FactorResult
  John A     2.4
  John B     1.5
  Ken  A     3
  </code></pre>
  
  <p>What would be the best way to do this? I am unsure on how to join these on two columns. I know I can join and then multiply the two columns, but I'm wondering if there is a better way than merging them first, then multiplying and dropping the unneeded columns?</p>