title: how to use pandas isin for multiple columns
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  <p>I want to find the values of <code>col1</code> and <code>col2</code> where the <code>col1</code> and <code>col2</code> of the first dataframe are both in the second dataframe.</p>
  
  <p>These rows should be in the result dataframe:</p>
  
  <ol>
  <li><p>pizza, boy</p></li>
  <li><p>pizza, girl</p></li>
  <li><p>ice cream, boy</p></li>
  </ol>
  
  <p>because all three rows are in the first and second dataframes.</p>
  
  <p>How do I possibly accomplish this? I was thinking of using <code>isin</code>, but I am not sure how to use it when I have to consider more than one column.</p>