title: How do I add a vertical line to a plotly gantt chart using pandas dataframe?
body: <p>I have a dataset with columns <code>Task</code> (<code>string</code> type),<code>Period_Min</code> and <code>Period_Max</code>. I would like to plot a classic gantt chart using <code>plotly</code> and add a vertical line for the special day <code>2017-12-31</code>. </p>
  
  <p>I've already tried the basic way to do it accordinf to plotly's official <a href="https://plot.ly/python/shapes/" rel="nofollow noreferrer">doc</a>. </p>
  
  <p>Here is my code:</p>
  
  <pre><code>fig=ff.create_gantt(data_user1,colors['#333F44','#93e4c1'],index_col='Diff_temps')
  layout = {
  'shapes': [
      # Line Vertical
      {
          'type': 'line',
          'x0': '2017-12-31',
          'y0': data_user1.Task.values[0],
          'x1': '2017-12-31',
          'y1': data_user1.Task.tail(1).values[0],
          'line': {
              'color': 'rgb(55, 128, 191)',
              'width': 3,
          }
      }
  ]
  }
  
  iplot(fig, layout)
  </code></pre>
  
  <p>Unfortunately, adding this particular <strong>layout</strong> doesn't change anything in my chart. Any help ?</p>