new_contents: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  """
  This example demonstrates a random walk with pyqtgraph.
  """
  
  import sys
  import numpy as np
  import pyqtgraph as pg
  from pyqtgraph.Qt import QtGui, QtCore
  from numpy_buffer import RingBuffer #  https://github.com/scls19fr/numpy-buffer
  
  class RandomWalkPlot:
      def __init__(self, win):
          #self.plot = pg.plot()
          self.plot = win.addPlot(title="Updating plot")
          
          self.ptr = 0
          
          #pen = 'r'
          pen = pg.mkPen('b', style=QtCore.Qt.SolidLine)
          self.curve = self.plot.plot(pen=pen, symbol='+')
          self.timer = QtCore.QTimer()
          self.timer.timeout.connect(self.update)
          self.timer.start(50)
          
          self.value = 1000 # initial value
          N = 100 # number of elements into circular buffer
          
          self.data_y = RingBuffer(N, self.value)
          
  
      def update(self):
          self.value += np.random.uniform(-1, 1)
  
          self.data_y.append(self.value)
          
          self.curve.setData(y=self.data_y) #  size is increasing up to N
          #self.curve.setData(y=self.data_y.all[::-1]) #  size is always N
          
          #if self.ptr == 0:
          #    self.plot.enableAutoRange('xy', False)  ## stop auto-scaling after the first data set is plotted
          #self.ptr += 1
  
  def main():
      #QtGui.QApplication.setGraphicsSystem('raster')
      app = QtGui.QApplication(sys.argv)
  
      #mw = QtGui.QMainWindow()
      #mw.resize(800,800)
  
      pg.setConfigOption('background', 'w')
      pg.setConfigOption('foreground', 'k')
  
      win = pg.GraphicsWindow(title="Basic plotting examples")
      win.resize(1000, 600)
      win.setWindowTitle('plot')
  
      # Enable antialiasing for prettier plots
      pg.setConfigOptions(antialias=True)
      
      upl = RandomWalkPlot(win)
      
      ## Start Qt event loop unless running in interactive mode or using pyside.
      if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
          QtGui.QApplication.instance().exec_()
  
  if __name__ == '__main__':
  	main()
  
subject: Add PyQtGraph random walk without datetime