title: Pandas - Replace None Value
body: <p>I get the data from database in my Python script and then storing the values in variables as follows:</p>
  
  <pre><code>df = pd.read_sql_query('EXEC script, dbcn)
  durationCurrent = df.loc[df['Indicator'] == 'Duration Current']['IndicatorValue'].values[0]
  </code></pre>
  
  <p>but sometimes the value returned is <code>None</code>.</p>
  
  <p>How to adjust the script to replace the <code>None</code> values for a custom string, e.g. <code>"Unknown"</code>?</p>