text: from datetime import datetime
  
  from vnpy.trader.ui import create_qapp, QtCore
  from vnpy.trader.database import database_manager
  from vnpy.trader.constant import Exchange, Interval
  from vnpy.chart import ChartWidget, VolumeItem, CandleItem
  
  if __name__ == "__main__":
      app = create_qapp()
  
      bars = database_manager.load_bar_data(
          "sc2103",
          Exchange.INE,
          interval=Interval.MINUTE,
          start=datetime(2021, 1, 1),
          end=datetime(2021, 1, 31)
      )
  
      widget = ChartWidget()
      widget.add_plot("candle", hide_x_axis=True)
      widget.add_plot("volume", maximum_height=200)
      widget.add_item(CandleItem, "candle", "candle")
      widget.add_item(VolumeItem, "volume", "volume")
      widget.add_cursor()
  
      n = 1000
      history = bars[:n]
      new_data = bars[n:]
  
      widget.update_history(history)
  
      def update_bar():
          bar = new_data.pop(0)
          widget.update_bar(bar)
  
      timer = QtCore.QTimer()
      timer.timeout.connect(update_bar)
      # timer.start(100)
  
      widget.show()
      app.exec_()
  