Pyqt 以OOP方式动画的效果改变自身窗体大小

代码：

 # -*- coding:utf8 -*-
 from PyQt4.QtGui import *
 from PyQt4.QtCore import *
 import sys

 class ani(QWidget):
     def __init__(self):
         super(ani, self).__init__()
         self.OrigHeight = 50
         self.ChangeHeight = 150
         self.setGeometry(QRect(500, 400, 150, self.OrigHeight))  # 在X=500， Y=400 ， Length=150 ,   Height=50
         self.btn = QPushButton(u'展开', self)
         self.btn.setGeometry(10, 10, 60, 35)
         self.machine = QStateMachine()
         self.connect(self.btn, SIGNAL('clicked()'), self.change)

     # 动画效果修改窗体大小
     def change(self):
         CurrentHeight = self.height()
         if self.OrigHeight == CurrentHeight:
             startHeight = self.OrigHeight
             endHeight = self.ChangeHeight
             self.btn.setText(u'收缩')
         else:
             startHeight = self.ChangeHeight
             endHeight = self.OrigHeight
             self.btn.setText(u'展开')
         self.animation = QPropertyAnimation(window, 'geometry')
         self.animation.setDuration(800)
         self.animation.setStartValue(QRect(500, 400, 150, startHeight))
         self.animation.setEndValue(QRect(500, 400, 150, endHeight))
         self.animation.start()

 if __name__ == '__main__':
     app = QApplication(sys.argv)
     window = ani()
     window.show()
     sys.exit(app.exec_())

效果：