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继承是指：可以使用现有类的所有功能，并在无需重新编写原来的类的情况下对这些功能进行扩展。
（1）通过继承创建的新类称为“子类”或“派生类”。
（2）被继承的类称为“基类”、“父类”或“超类”。
继承的过程，就是从一般到特殊的过程。要实现继承，可以通过“继承”（Inheritance）和“组合”（Composition）来实现。
在某些 OOP 语言中，一个子类可以继承多个基类。但是一般情况下，一个子类只能有一个基类，要实现多重继承，可以通过多级继承来实现。

2、继承的分类

继承概念的实现方式主要有2类：实现继承、接口继承。

（1）实现继承是指使用基类的属性和方法而无需额外编码的能力；
（2）接口继承是指仅使用属性和方法的名称、但是子类必须提供实现的能力(子类重构父类方法)；
在考虑使用继承时，有一点需要注意，那就是两个类之间的关系应该是“属于”关系。
抽象类仅定义将由子类创建的一般属性和方法。
OO开发范式大致为：划分对象→抽象类→将类组织成为层次化结构(继承和合成) →用类与实例进行设计和实现几个阶段。

3、示例代码

#!/usr/bin/env Python# -*- coding:utf-8 -*-# Author:ZhengzhengLiu#类的继承class People: def __init__(self,name,age):  self.name = name  self.age = age def eat(self):  print("%s is eating..." %self.name) def sleep(self):  print("%s is sleeping..." %self.name) def talk(self):  print("%s is talking..." %self.name)class Man(People):  #继承父类People类 def make_money(self):  print("%s is making money..." %self.name) def sleep(self):  People.sleep(self)  #对父类方法的扩展  print("man is sleeping...")class Women(People): def shop(self):  print("%s is shopping..." %self.name)m1 = Man("Jack","20")m1.eat()m1.make_money()m1.sleep()w1 = Women("Amy","25")w1.talk()w1.shop()

运行结果：

Jack is eating...
Jack is making money...
Jack is sleeping...
man is sleeping...
Amy is talking...
Amy is shopping...

4、子类中对父类的构造函数进行重构两种方法

#!/usr/bin/env python# -*- coding:utf-8 -*-# Author:ZhengzhengLiu#类的继承#class People:  #经典类class People(object):  #新式类 def __init__(self,name,age):  self.name = name  self.age = age def eat(self):  print("%s is eating..." %self.name) def sleep(self):  print("%s is sleeping..." %self.name) def talk(self):  print("%s is talking..." %self.name)class Man(People):  #继承父类People类 def __init__(self,name,age,money):  #People.__init__(self,name,age)  #(方法一)对构造函数进行重构、添加父类中没有的属性  super(Man,self).__init__(name,age) #(方法二)利用super对构造函数进行重构（新式类写法）  self.money = money  print("%s have money %s$" %(self.name,self.money)) def make_money(self):  print("%s is making money..." %self.name) def sleep(self):  People.sleep(self)  #对父类方法的扩展  print("man is sleeping...")class Women(People): def shop(self):  print("%s is shopping..." %self.name)m1 = Man("Jack","20",10)m1.eat()m1.make_money()m1.sleep()w1 = Women("Amy","25")w1.talk()w1.shop()

运行结果：

J ack have money 10$
Jack is eating...
Jack is making money...
Jack is sleeping...
man is sleeping...
Amy is talking...
Amy is shopping...

5、多继承方式

#!/usr/bin/env python# -*- coding:utf-8 -*-# Author:ZhengzhengLiu#类的继承#class People:  #经典类class People(object):  #新式类 def __init__(self,name,age):  self.name = name  self.age = age  self.friends = [] def eat(self):  print("%s is eating..." %self.name) def sleep(self):  print("%s is sleeping..." %self.name) def talk(self):  print("%s is talking..." %self.name)class Relationship(object): def make_friends(self,obj):  print("%s is making friends with %s" %(self.name,obj.name))  self.friends.append(obj)class Man(People,Relationship):  #多继承 def __init__(self,name,age,money):  #People.__init__(self,name,age)  #(方法一)对构造函数进行重构、添加父类中没有的属性  super(Man,self).__init__(name,age) #(方法二)利用super对构造函数进行重构（新式类写法）  self.money = money  print("%s have money %s$" %(self.name,self.money)) def make_money(self):  print("%s is making money..." %self.name) def sleep(self):  People.sleep(self)  #对父类方法的扩展  print("man is sleeping...")class Women(People,Relationship): #多继承 def shop(self):  print("%s is shopping..." %self.name)m1 = Man("Jack","20",10)w1 = Women("Amy","25")m1.make_friends(w1)w1.name = "liu"print(m1.friends)

运行结果：

Jack have money 10$
Jack is making friends with Amy
[<__main__.Women object at 0x0057FA30>]

6、新式类与经典类的继承顺序

#!/usr/bin/env python# -*- coding:utf-8 -*-# Author:ZhengzhengLiuclass A(object):#新式类 def __init__(self):  print("A")class B(A): def __init__(self):    print("B")class C(A): def __init__(self):  print("C")class D(B,C): def __init__(self):  pass  #print("D")obj = D()

7、继承示例——学校、教师与学生

#!/usr/bin/env python# -*- coding:utf-8 -*-# Author:ZhengzhengLiu#继承实例(新式类)——模拟学校、教师与学生class School(object): def __init__(self,name,addr):  self.name = name  self.addr = addr  self.students = []  self.stuffs = [] def enroll(self,stu_obj):  #学生注册  print("%s 学员办理注册" %stu_obj.name)  self.students.append(stu_obj) def heir(self,staff_obj):  #聘请教师  print("聘请教师 %s" %staff_obj.name)  self.stuffs.append(staff_obj)class SchoolMember(object): def __init__(self,name,age,sex):  self.name = name  self.age = age  self.sex = sex def tell(self):  passclass Teacher(SchoolMember): def __init__(self,name,age,sex,salary,course):  super(Teacher,self).__init__(name,age,sex)  self.salary = salary  self.course = course def tell(self):  print('''  ----- info of Teacher:%s -----  Name:%s  Age:%s  Sex:%s  Salary:%s  Course:%s  '''%(self.name,self.name,self.age,self.sex,self.salary,self.course)) def teach(self):  print("%s is teaching course [%s]" %(self.name,self.course))class Student(SchoolMember): def __init__(self,name,age,sex,stu_id,grade):  super(Student,self).__init__(name,age,sex)  self.stu_id = stu_id  self.grade = grade def tell(self):  print('''  ----- info of Student:%s -----  Name:%s  Age:%s  Sex:%s  Stu_id:%s  Grade:%s  '''%(self.name,self.name,self.age,self.sex,self.stu_id,self.grade)) def pay_tuition(self,amount):  print("%s has paied tuition for $%s" %(self.name,amount))#实例化school = School("qinghua","beijing")t1 = Teacher("Jack","30","M","20000","Python")t2 = Teacher("Amy","28","F","15000","Linux")s1 = Student("liu","23","M","1701","Python")s2 = Student("wang","25","F","1702","Linux")#调用显示学生与教师的信息t1.tell()s1.tell()school.heir(t1)  #聘请教师t1school.enroll(s1) #学生s1注册school.enroll(s2)print(school.stuffs)print(school.students)#聘请的第一位教师教课school.stuffs[0].teach()for stu in school.students: stu.pay_tuition(5000)

运行结果：

----- info of Teacher:Jack -----
Name:Jack
Age:30
Sex:M
Salary:20000
Course:Python

----- info of Student:liu -----
Name:liu
Age:23
Sex:M
Stu_id:1701
Grade:Python

聘请教师 Jack
liu 学员办理注册
wang 学员办理注册
[<__main__.Teacher object at 0x0059FDB0>]
[<__main__.Student object at 0x0059FDF0>, <__main__.Student object at 0x0059FE10>]
Jack is teaching course [Python]
liu has paied tuition for $5000
wang has paied tuition for $5000

8、多态（polymorphisn）——一种接口，多种形态

（1）定义

多态性（polymorphisn）是允许你将父对象设置成为和一个或更多的他的子对象相等的技术，

赋值之后，父对象就可以根据当前赋值给它的子对象的特性以不同的方式运作。

简单的说，就是一句话：允许将子类类型的指针赋值给父类类型的指针。

多态的作用：我们知道，封装可以隐藏实现细节，使得代码模块化；继承可以扩展已存在的代码模块（类）；它们的目的都是为了——代码重用。

而多态则是为了实现另一个目的——接口重用！多态的作用，就是为了类在继承和派生的时候，保证使用“家谱”中任一类的实例的某一属性时的正确调用。

Pyhon 很多语法都是支持多态的，比如 len(),sorted(), 你给len传字符串就返回字符串的长度，传列表就返回列表长度。

（2）示例代码：

#!/usr/bin/env python# -*- coding:utf-8 -*-# Author:ZhengzhengLiuclass Animal(object): def __init__(self,name):  self.name = name def talk(self):  raise NotImplementedError("Subclass must implement abstract method") # 多态——一种接口，多种形态 @staticmethod def animal_talk(obj):  obj.talk()class Cat(Animal): def talk(self):  print("%s Meow!" %self.name)class Dog(Animal): def talk(self):  print("%s Woof! Woof!" % self.name)d = Dog("A")#d.talk()c = Cat("B")#c.talk()#多态Animal.animal_talk(d)Animal.animal_talk(c)

运行结果：