python vtk 通过回调函数监测键盘”Up”键动作，每按一次方向上键，actor变换一种颜色

import vtk
 
class KeyPressInteractorStyle(vtk.vtkInteractorStyleTrackballCamera):
 
    def __init__(self,parent=None):
        self.parent = vtk.vtkRenderWindowInteractor()
        if(parent is not None):
            self.parent = parent
 
        self.AddObserver("KeyPressEvent",self.keyPress)
 
    def keyPress(self,obj,event):
        key = self.parent.GetKeySym()
        if key == 'Up':
            #产生随机颜色
            r = vtk.vtkMath.Random(., 1.0)
            g = vtk.vtkMath.Random(., 1.0)
            b = vtk.vtkMath.Random(., 1.0)
            actor.GetProperty().SetColor(r, g, b)
            #下面这一行是关键，实现了actor的更新
            renWin.Render()
 
#在此处修改几何类型
cube = vtk.vtkCubeSource()
 
mapper = vtk.vtkPolyDataMapper()
mapper.SetInputConnection(cube.GetOutputPort())
 
actor = vtk.vtkActor()
actor.SetMapper(mapper)
#修改actor初始颜色
actor.GetProperty().SetColor(1.0, 1.0, 1.0)
#修改actor初始状态旋转角度
actor.RotateX(30.0)
actor.RotateY(-45.0)
 
ren = vtk.vtkRenderer()
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(ren)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)
 
iren.SetInteractorStyle(KeyPressInteractorStyle(parent = iren))
 
ren.AddActor(actor)
#修改背景颜色
ren.SetBackground(0.1, 0.2, 0.3)
#修改窗口大小
renWin.SetSize(, )
 
iren.Initialize()
 
ren.ResetCamera()
ren.GetActiveCamera().Zoom(1.5)
renWin.Render()
 
iren.Start()