title: Pandas: LEFT OUTER JOIN where (ON) 2 Conditions that Match
body: <p>I have 2 Dataframes that I'd like to combine in Pandas where two 2 conditions are met, but I'm not successfully getting there. Thanks in advance for assistance!</p>
  
  <pre><code>df1
      A    B    C
  0   1    2    3
  1   4    5    6
  2   7    8    9
  
  df2
      A    B    F
  0   1    2    cat
  1   4    5    dog
  2   7    8    moose
  </code></pre>
  
  <h3>Desired Result</h3>
  
  <pre><code>df3
      A    B    C    F
  0   1    2    3    cat
  1   4    5    6    dog
  2   7    8    9    moose
  </code></pre>
  
  <p>Attempts to <code>merge</code> that are failing that are failing:</p>
  
  <ul>
  <li><code>pd.merge(df1, df2, on='A' &amp; 'B', how='left')</code> </li>
  <li><code>pd.merge(df1, df2, on('A' &amp; 'B'), how='left')</code> </li>
  <li><code>pd.merge(df1, df2, on='A' &amp; on='B',how='left')</code></li>
  </ul>