title: fill column from values of two other columns
body: <p>I have a data frame of two columns col1 and col2 I want to fill column 3 from value col1 and col2.</p>
  
  <pre><code>df['col3'] = "122 (xxxxx): Don't show temp df['col1'] and df['col2']"
  </code></pre>
  
  <p>Does anyone knows how to do please?</p>