code: from PyQt4 import QtGui,QtCore
  import sys
  import ui_main
  import numpy as np
  import pylab
  import time
  import pyqtgraph
  
  class ExampleApp(QtGui.QMainWindow, ui_main.Ui_MainWindow):
      def __init__(self, parent=None):
          pyqtgraph.setConfigOption('background', 'w') #before loading widget
          super(ExampleApp, self).__init__(parent)
          self.setupUi(self)
          self.btnAdd.clicked.connect(self.update)
          self.grPlot.plotItem.showGrid(True, True, 0.7)
  
      def update(self):
          t1=time.clock()
          points=100 #number of data points
          X=np.arange(points)
          Y=np.sin(np.arange(points)/points*3*np.pi+time.time())
          C=pyqtgraph.hsvColor(time.time()/5%1,alpha=.5)
          pen=pyqtgraph.mkPen(color=C,width=10)
          self.grPlot.plot(X,Y,pen=pen,clear=True)
          print("update took %.02f ms"%((time.clock()-t1)*1000))
          if self.chkMore.isChecked():
              QtCore.QTimer.singleShot(1, self.update) # QUICKLY repeat
  
  if __name__=="__main__":
      app = QtGui.QApplication(sys.argv)
      form = ExampleApp()
      form.show()
      form.update() #start with something
      app.exec_()
      print("DONE")
apis: numpy.arange