title: join two CSVs by IDs
body: <p>I have two CSV files like:</p>
  
  <p>first.csv:</p>
  
  <pre><code>1,A B C
  2,A D
  3,T Q
  </code></pre>
  
  <p>second.csv:</p>
  
  <pre><code>1,
  2,P A
  3,
  4,A O
  </code></pre>
  
  <p>Is is possible to join these two CSVs to make a CSV in similar format using pandas?</p>
  
  <p>The output CSV should be like:</p>
  
  <pre><code>1,A B C
  2,A D P
  3,T Q
  4,A O
  </code></pre>