class Program(object):

     def __init__(self,name,age,weigth):

         self.name=name

         self._age=age

         self.__weight=weigth

     def getWeight(self):

         return self.__weight

 if __name__ == '__main__':

     a=Program("alex",23,45)

     print a

     print dir(a)

     print a.getWeight()

     print a._Program__weight#python 的私有属性的定义