title: First update of plotly Dash with live update
body: <p>I am trying to use live update with plotly Dash (0.18.3) in Python (3.x), but I don't need to update the plot so often (once or twice a day is what I need).</p>
  
  <p>I did the following so far:</p>
  
  <pre><code>import dash
  import pandas as pd
  import plotly.graph_objs as go
  import dash.dependencies as ddp
  import dash_core_components as dcc
  import dash_html_components as html
  
  def plot_figure(data):
      layout = dict(
      title="Figure w/ plotly",
      )
  
      fig = dict(data=data, layout=layout)
      return fig
  
  def serve_layout():
      return html.Div(children=[
          html.Div([
              html.H1("Plotly test with Live update",
                      style={"font-family": "Helvetica",
                             "border-bottom": "1px #000000 solid"}),
              ], className='banner'),
          html.Div([dcc.Graph(id='plot')],),
          dcc.Interval(id='live-update', interval=interval),
  ],)
  
  second = 1000
  minute = 60
  hour   = 60
  day    = 24
  interval = 1/2*day*hour*minute*second
  
  app = dash.Dash()
  
  app.layout = serve_layout
  
  @app.callback(
      ddp.Output('plot', 'figure'),
      [],
      [],
      [ddp.Event('live-update', 'interval')])
  def gen_plot():
      ind = ['a', 'b', 'c', 'd']
      df = pd.DataFrame({'one' : pd.Series([4., 3., 2., 1.], index=ind),
                         'two' : pd.Series([1., 2., 3., 4.], index=ind)})
  
      trace = [go.Scatter(x=df.index, y=df['one'])]
      fig   = plot_figure(trace)
      return fig
  
  if __name__ == '__main__':
      app.run_server(debug=True)
  </code></pre>
  
  <p>The problem is at first nothing appears, it updates only after <code>interval</code>, so after half a day. I added the <code>serve_layout</code> function following <a href="https://plot.ly/dash/live-updates" rel="nofollow noreferrer">Dash documentation</a> to have an update when the page is loaded, but it seems to have no effect.</p>
  
  <p>How could I have a first update when the page is first accessed and then updates at every <code>interval</code>?</p>