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>