class SketchWindow(wx.Window):

  def __init__(self, parent):
    wx.Window.__init__(self, parent, -1)
    self.SetBackgroundColour('White')
    # Window event binding
    self.Bind(wx.EVT_PAINT, self.OnPaint)
    self.Bind(wx.EVT_IDLE, self.OnIdle)
    # run
    self.Run()

  def OnPaint(self, evt):
    self.DrawEntities(wx.PaintDC(self))

  def DrawEntities(self, dc):
    dc.SetPen(wx.Pen('Black', 1, wx.SOLID))
    dc.SetBrush(wx.Brush('Green', wx.SOLID))
    # draw all
    for e in self.entities:
      x, y = e.location
      dc.DrawCircle(x, y, 4)

  def OnIdle(self, event):
    self.Refresh(False)

  def Run(self):
    # update self.entities ...
    # call this method again later
    wx.CallLater(50, self.Run)