__xxx

#!/usr/bin/python3
#-*- coding:utf-8 -*-


class Student:
  def __init__(self,name,score):
    self.name = name
    self.__score = score #将score隐藏起来，使之仅在类内部可用。

  def __show(self):    #一个隐藏的方法，同样只在内部可用
    print(self.name,self.__score)#使用被隐藏的属性__score
    
  def Show(self):
    self.__show()    #注意被隐藏方法的调用方式。


  
def main():
  he = Student('Bob',95)
  he.Show()       #显示：Bob 95
  #print(he.__score)   #AttributeError: 'Student' object has no attribute '__score'
  #he.__show()      #AttributeError: 'Student' object has no attribute '__show'

  #隐藏属性真的被隐藏了吗？其实仍然可使用，使用格式 obj._className__attributeName
  #但是仅仅作为了解，不建议使用隐藏属性。
  print(he._Student__show())  #显示：Bob 95
  print(he._Student__score)   # 显示： 95
  
  
  

if __name__=="__main__":
  main()

#!/usr/bin/python3
#-*- coding:utf-8 -*-


class Student:
  def __init__(self,name,score):
    self.name = name
    self.score = score 

  @property        #实现属性的读取方法，读取实例的score值时，就会调用这个函数
  def score(self):
    return self.__score

  
  @score.setter     #实现属性写入方法，写入实例的score属性时，调用这个函数
  def score(self,newVal):
    if not isinstance(newVal,(int,float)):
      raise TypeError('score value must be a number')
    if newVal>100 or newVal<0:
      raise ValueError('score value must between 0 and 100')

    self.__score = newVal

  

  
def main():
  he = Student('Bob',95)
  he.score = 100   #重新写入 

  
  print(he.score)  #读取   
    
  

if __name__=="__main__":
  main()

#!/usr/bin/python3
#-*- coding:utf-8 -*-


class Student:
  def __init__(self,name,score):
    self.name = name
    self.score = score 

 

  
def main():
  he = Student('Bob',95)
  he.age = 19
  print(he.age)
  

if __name__=="__main__":
  main()

使用__slots__



#!/usr/bin/python3
#-*- coding:utf-8 -*-


class Student:
  __slots__ = ('name','score') #将属性名以字符串形式加入元组
  def __init__(self,name,score):
    self.name = name
    self.score = score 

 

  
def main():
  he = Student('Bob',95)
  he.age = 19  #AttributeError: 'Student' object has no attribute 'age'
  print(he.age)
  

if __name__=="__main__":
  main()