day06-2-Python面向对象特性：继承

 

• 面向对象编程 (OOP) 语言的一个主要功能就是“继承”。继承是指这样一种能力：它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。

  通过继承创建的新类称为“子类”或“派生类”。

  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。

  继承概念的实现方式主要有2类：实现继承、接口继承。

  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；
  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(子类重构爹类方法)；
  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。例如，Employee 是一个人，Manager 也是一个人，因此这两个类都可以继承 Person 类。但是 Leg 类却不能继承 Person 类，因为腿并不是一个人。
• 单继承

• # 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 talk(self):
          print("%s is talking..." % self.name)
  
  
      def sleep(self):
          print("%s is sleeping..." % self.name)
  
  class Man(People):
      def __init__(self, name, age, money):
  # People.__init__(self,name,age)或者
  # 经典类写法
          super(Man, self).__init__(name, age)
          self.money = money
          print("重构对象添加新属性：%s" % self.money)
  def piao(self):
      print("%s is piaoing ..... 20s....done." % self.name)
  def sleep(self):
      People.sleep(self)
  print("man is sleeping ")
  # Yang is sleeping...
  # man is sleeping
  m1 = Man("Yang", 22, 10)
  m1.eat()
  m1.sleep()
  class Woman(People):
      def get_birth(self):
          print("%s is born a baby...." % self.name)
  w1 = Woman("Chen", 26)
  w1.get_birth()
  # 输出结果
  # 重构对象添加新属性：10
  # Yang is eating...
  # Yang is sleeping...
  # man is sleeping
  # Chen is born a baby....

   

• 多继承

• class A:
      def __init__(self):
          print("A")
  class B(A):
      pass
      # def __init__(self):
      #     print("B")
  class C(A):
      pass
      # def __init__(self):
      #     print("C")
  class D(B,C):#只初始化B的__init__函数，不走C就停止
      pass
      # def __init__(self):
      #     print("D")
  obj = D()
  # 多继承：两中查找方式（广度优先，深度优先），默认广度优先
  # Python2：经典类：深度优先，新式类广度优先
  # python3：广度优先

  
  
  

案例：继承——学校

 

__author__ = "Alex Li"

class School(object):
    def __init__(self,name,addr):
        self.name = name
        self.addr = addr
        self.students =[]
        self.staffs =[]
    def enroll(self,stu_obj):
        print("为学员%s 办理注册手续"%stu_obj.name )
        self.students.append(stu_obj)
    def hire(self,staff_obj):
        self.staffs.append(staff_obj)
        print("雇佣新员工%s" % staff_obj.name)

class SchoolMember(object):
    def __init__(self,name,age,sex):
        self.name = name
        self.age = age
        self.sex = sex
    def tell(self):
        print("tell:")

class 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 paid tution for $%s"% (self.name,amount) )


school = School("IT","火星")

t1 = Teacher("zlz",56,"MF",200000,"Linux")
t2 = Teacher("zlf",22,"M",3000,"PythonDevOps")

s1 = Student("张路风",36,"MF",1001,"PythonDevOps")
s2 = Student("雷大侠",19,"M",1002,"Linux")


t1.tell()
s1.tell()
school.hire(t1)
school.enroll(s1)
school.enroll(s2)

print(school.students)
print(school.staffs)
school.staffs[0].teach()

for stu in school.students:
    stu.pay_tuition(5000)

##########################################################################################################

#输出：

---- info of Teacher:zlz ----

Name:zlz

Age:56

Sex:MF

Salary:200000

Course:Linux

---- info of Student:张路风 ----

Name:张路风

Age:36

Sex:MF

Stu_id:1001

Grade:PythonDevOps

雇佣新员工zlz

为学员张路风 办理注册手续

为学员雷大侠 办理注册手续

[<__main__.Student object at 0x0000000002244668>, <__main__.Student object at 0x00000000022446A0>]

[<__main__.Teacher object at 0x00000000022445F8>]

zlz is teaching course [Linux]

张路风 has paid tution for $5000

雷大侠 has paid tution for $5000