3、继承应用原理、组合

子类派生的新方法中重用父类的功能

继承实现原理（菱形问题）

多继承代码规范

组合

子类派生的新方法中重用父类的功能

  class People：
        school = '上海校区'
        
        def __init__(self,name,age,sex)
              self.name = name
              self.age = age
              self.sex = sex
  class Student(people):
        def choose(self)
              print('%s 选课成功' %self.name)

  class Teacher(People):
        def __init__(self,name,age,sex,level):
              People.__init__(self,name,age,sex,)
              self.levle = level
        
        def course(self):
              print('%s 正在打分'%self.name)

  s = Student('liu',18,'male')
  print(s.__dict__)    # {'name': 'liu', 'age': 18, 'sex': 'male'}
  print(s.name)       # liu
  s.choose()          # liu 正在选课

  t= Teacher('egon',18,'male',8999,9000000)
  print(t.__dict__) #{'name': 'egon', 'age': 18, 'sex': 'male', 'level': 8999, 'salary': 9000000}

People.init(self)直接调用，不继承也可以

super调用 总体代码和上面一样，再敲一遍

  class People:
        school = '天上人间'
        def __init__(self,name,age,sex)
              self.name = name
              self.age = age
              self.sex = sex
  class Student(People):   
        def choose(self)
              print('%s 选课中' %self.name)
  class Teacher(People):    # 使用super调用，必须继承
        def __init__(self,name,age,sex,level,salary)
              # super(Teacher, self).__init__()    # 可省略Teacher,self
              super().__init__(name,age,gender)  # 且不需传self
              self.level = level
              self.salary = salary
        def course(self):
              print('%s 打分'%self.name)
  s = Student('liu',18,'male')
  print(s.__dict__)    # {'name': 'liu', 'age': 18, 'sex': 'male'}
  print(s.name)       # liu
  s.choose()          # liu 正在选课

  t= Teacher('egon',18,'male',8999,9000000)
  print(t.__dict__) #{'name': 'egon', 'age': 18, 'sex': 'male', 'level': 8999, 'salary': 9000000}
  # 调用同上

==继承实现原理（菱形问题）

  一个子类继承的多分枝最终汇聚一个非object的类上
  class G: # 在python2中，未继承object的类及其子类，都是经典类
      def test(self):
          print('from G')

  class E(G):
      def test(self):
          print('from E')

  class F(G):
      def test(self):
          print('from F')

  class B(E):
        def test(self):
        print('from B')

  class C(F):
        def test(self):
        print('from C')

  class D(G):
        def test(self):
        print('from D')

  class A(B,C,D):
        def test(self):
        print('from A')
        obj = A()  # A->B->E->C->F->D->G->object 按照这个顺序也就是mro列表继承

多继承规范

  涉及到多继承 可用mixins机制，如下
  class Vehicle:
        pass

  class FlyableMixin:
        def fly(self):
        print('flying')

  class CivilAircraft(FlyableMixin,Vehicle):
        pass

  class Helicopter(FlyableMixin,Vehicle):
          
  class Car(Vehicle):
      pass

组合，表示有，继承是 是 的关系，比如 人是动物，组合是 有 的关系，比如 我有手机，

  class People:
        school = '天上人间'
        def __init__(self,name,age,gender)
              self.name = name
              self.age = age
              self.gender = gender
              
  class Student(People):
        def choose(self):
              print('%s 选课'%self.name)

  class Teacher(People):
        def __init__(self,name,age,gender,level,salary)
              super().__init(name,age,gender)
              self.level = level
              self.gender = gender
        def score(self):
              print('%s正在打分'%self.name)


  class Course:
        def __init__(self,name,price,proide)
              self.name = name
              self.price = price
              self.proide = proide
        def tell(self):
              print('课程信息<%s:%s:%s>'%s(self.name,self.price,self.proide)
  python = ('全栈开发'，20000，'6mons')
  linux = ('运维'，19999,'5mons')
  s1 = Student('liu',18,'male')
  t1 = Teacher('egon',18,'male')
  
  s1.course = []
  s1.course.append(python)
  s1.course.append(linux)
  for course_obj1 in s1.course:
        course_obj1.tell()      #课程信息<开发:19999:6mons>  课程信息<运维:19998:5mons>