title: Replace empty rows pandas
body: <p>I have some empty rows in <code>Bidfloor df_g column</code> so I want to change they with <code>floorprice</code></p>
  
  <p>the problem is if I do this: <code>df_g.loc[df_g['Bidfloor'] == 0, 'Bidfloor'] = floorprice</code> the funtion works but I don't have 0 in the rows, so I'm tring with: <code>df_g.loc[df_g['Bidfloor'] == '', 'Bidfloor'] = floorprice</code> to simulate the empty row but I have this error: <code>TypeError: invalid type comparison</code></p>
  
  <pre><code>floorprice = 0.2
  df_g.loc[df_g['Bidfloor'] == '', 'Bidfloor'] = floorprice
  </code></pre>