python编程面向对象类（2）

　　(11) 成员可见性公开和私有
　　类的方法也可以调用方法class StudentClass:     school_sum = 100      def __init__(self, name, age):         self.name = name         self.age = age      def have_class(self):         print(＂have class＂)      def have_english_class(self):         self.have_class()         print(＂have english class＂)   student1 = StudentClass(＂cici＂, 18) student1.have_english_class()  输出： have class have english class
　　类的变量和方法可以被对象调用，不具备安全性。
　　对象更改、建议在内部方法做判断，保证安全性。class StudentClass:     school_sum = 100      def __init__(self, name, age):         self.name = name         self.age = age         self.score = 0      def class_score(self, score):         if self.score == 0:             print(＂不允许更改＂)         else:             self.score = score         print(self.score)   student1 = StudentClass(＂cici＂, 18) student1.class_score(100)  输出： 不允许更改 0
　　因为变量是公开的，所以可以访问和赋值，私有的则不可以。
　　表示私有：__ 双下划綫写在名字开头class StudentClass:     school_sum = 100      def __init__(self, name, age):         self.name = name         self.age = age         self.score = 0      def __class_score(self, score):         if self.score == 0:             print(＂不允许更改＂)         else:             self.score = score         print(self.score)   student1 = StudentClass(＂cici＂, 18) student1.class_score(100)  输出： AttributeError: ＂StudentClass＂ object has no attribute ＂class_score＂
　　通过点，给student1加上一个属性class StudentClass:     school_sum = 100      def __init__(self, name, age):         self.name = name         self.age = age         self.__score = 0      def __class_score__(self, score):         if self.score == 0:             print(＂不允许更改＂)         else:             self.score = score         print(self.score)   student1 = StudentClass(＂cici＂, 18) student1.__score = 100  # 通过点，给student1加上一个属性 student1.aaa = ＂aaa＂ print(student1.aaa) print(student1.__score) print(student1.__dict__)  student2 = StudentClass(＂cici＂, 18) print(student2.__dict__)  输出： aaa 100 {＂name＂: ＂cici＂, ＂age＂: 18, ＂_StudentClass__score＂: 0, ＂__score＂: 100, ＂aaa＂: ＂aaa＂} {＂name＂: ＂cici＂, ＂age＂: 18, ＂_StudentClass__score＂: 0}
　　(12) 没有什么是不能访问
　　python是没有严格意义上的私有变量的，可以通过被更换过后的名字获得class StudentClass:     school_sum = 100      def __init__(self, name, age):         self.name = name         self.age = age         self.__score = 0      def __class_score__(self, score):         if self.score == 0:             print(＂不允许更改＂)         else:             self.score = score         print(self.score)   student1 = StudentClass(＂cici＂, 18) student1.__score = 100  # 通过点，给student1加上一个属性 print(student1._StudentClass__score)  输出： 0
　　(13) 继承
　　面向对象三大特性：继承性、封装性、多态性# 在d1中的脚本 class Human:     human_sum = 100      def __init__(self, name, age):         self.name = name         self.age = age      def get_name(self, score):         print(self.name)# 在d2的脚本 from d1 import Human   class StudentClass(Human):     def have_class(self):         print(＂have class＂)   print(StudentClass.human_sum) # 继承了父类的__init__ student1 = StudentClass(＂cici＂, 18) # 继承了父类的变量 print(student1.human_sum) print(student1.name) print(student1.age)  输出： 100 100 cici 18
　　(14) 子类方法调用父类方法super关键字# 在d1中的脚本 class Human:     human_sum = 100      def __init__(self, name, age):         self.name = name         self.age = age      def get_name(self, score):         print(self.name) # 在d2的脚本 from d1 import Human   class StudentClass(Human):     def __init__(self, school, name, age):         self.school = school         # 在子类里面调用父类的构造函数         Human.__init__(self, name, age)      def have_class(self):         print(＂have class＂)   # 继承了父类的__init__ student1 = StudentClass(＂第一中学＂, ＂cici＂, 18) # 继承了父类的变量 print(student1.school) print(student1.name) print(student1.age)
　　Human.__init__(self, name, age) 在类里调用实例方法是没有意义的。
　　没有通过实例对象来调用，所以需要加上self。class StudentClass(Human):     def __init__(self, school, name, age):         self.school = school         Human.__init__(self, name, age)      def have_class(self):         print(＂have class＂)   StudentClass.have_class()  输出： TypeError: StudentClass.have_class() missing 1 required positional argument: ＂self＂class StudentClass(Human):     def __init__(self, school, name, age):         self.school = school         # 在子类里面调用父类的构造函数         Human.__init__(self, name, age)      def have_class(self):         print(＂have class＂)  StudentClass.have_class(student1) #这样多此一举  输出： have class
　　主流的调用父类方法的方式：super(子类名字, self).__init__()# 在d1的脚本 class Human:     human_sum = 100      def __init__(self, name, age):         self.name = name         self.age = age      def have_class(self):         print(＂have class :  Human＂) # 在d2的脚本 from d1 import Human   class StudentClass(Human):     def __init__(self, school, name, age):         self.school = school         super(StudentClass, self).__init__(name, age)      def have_class(self):         print(＂have class : StudentClass＂)         super(StudentClass, self).have_class() # 可以在方法里调用父类的方法   # 继承了父类的__init__ student1 = StudentClass(＂第一中学＂, ＂cici＂, 18) print(student1.school) print(student1.name) print(student1.age) student1.have_class()  # 优先调用子类方法  输出： 第一中学 cici 18 have class : StudentClass have class :  Human