title: How to multiply two columns of a pandas data-frame (row multiplication) and store the result in a new column?
body: <p>Command </p>
  
  <p><code>df_main['Ranking'] = df_main['Porosity']*['Permeability']</code> gives - </p>
  
  <blockquote>
    <p>TypeError: can't multiply sequence by non-int of type 'str'</p>
  </blockquote>
  
  <p>The attacehd picture (<a href="https://i.stack.imgur.com/0Asu3.png" rel="nofollow noreferrer">https://i.stack.imgur.com/0Asu3.png</a>) has more information. My code snippet is at i.stack.imgur.com/ehqF5.png)</p>
  
  <p>More info: <a href="https://i.stack.imgur.com/0Asu3.png" rel="nofollow noreferrer">https://i.stack.imgur.com/0Asu3.png</a></p>