title: Is there a way of summing specific columns if they exist in a list?
body: <p>I'm trying to lookup a column in df2 and only sum the columns in df1 that exist in the df2 column</p>
  <pre class="lang-py prettyprint-override"><code>df1 =
  London, New York, Paris, LA, Chicago
  1000, 2000, 5000, 10000, 3000
  
  df2 =
  US Cities
  New York
  Miami
  LA
  Chicago
  Seattle 
  </code></pre>
  <p>result:</p>
  <pre class="lang-py prettyprint-override"><code>df1 =
  London, New York, Paris, LA, Chicago, Sum of US Cities
  1000, 2000, 5000, 10000, 3000, 15000
  </code></pre>