day23

初识继承

字面意思：儿子可以完全使用父亲的所有内容

专业角度：如果B类继承A类，

B类就称为子类、派生类

A类就称为父类、基类、超类

面向对象三大特性：继承、封装、多态

继承：单继承、多继承

# class Human:

#     def __init__(self, name, sex, age):

#         self.name = name

#         self.age = age

#         self.sex = sex

#

#

# class Dog:

#     def __init__(self, name, sex, age):

#         self.name = name

#         self.age = age

#         self.sex = sex

#

#

# class Cat:

#     def __init__(self, name, sex, age):

#         self.name = name

#         self.age = age

#         self.sex = sex

				继承

class Animal:

    def __init__(self, name, sex, age):

        self.name = name

        self.age = age

        self.sex = sex

class Human(Animal):

    pass

class Dog(Animal):

    pass

class Cat(Animal):

    pass

# Human,Dog,Cat 子类、派生类

# Animal 父类、基类、超类

person = Human("李业", "男", 18)

print(person.name)

继承的优点

  • 减少了重复代码
  • 增加了类的耦合性（耦合性不宜多，宜精）
  • 使得代码更加规范化，合理化

单继承

  • 类名执行父类属性方法
class Animal:

    live = "有生命的"

    def __init__(self, name, sex, age):

        self.name = name

        self.age = age

        self.sex = sex

    def eat(self):

        print("动物都需要进食")

class Human(Animal):

    live = "有思想的活着"

# 1、类名执行父类属性方法

print(Human.live)

Human.eat(111)
  • 对象执行父类属性方法

    查询顺序单向不可逆: 子类使用父类的属性方法,父类不能使用子类的属性方法.

class Animal:

    live = "有生命的"

    def __init__(self, name, sex, age):

        self.name = name

        self.age = age

        self.sex = sex

    def eat(self):

        print(self)

        print("动物都需要进食")

class Human(Animal):

    body = "有头有脸"

# 2、子类对象执行父类的属性方法

obj = Human('汪洋', '男', 48)

print(obj.live)

obj.eat()

print(obj)

# a1 = Animal('汪洋', '男', 48)

# print(a1.body)  # 报错，父类不能获取子类属性
  • 在子类中既执行子类方法又执行父类方法

方法一：不依赖继承的

# class Animal:

#     def __init__(self, name, sex, age):

#         self.name = name

#         self.age = age

#         self.sex = sex

#

#

# class Human:

#    def __init__(self,name, sex, age, hobby):

#        '''

#

#        :param name: 李业

#        :param sex: 男

#        :param age: 18

#        :param hobby: 旅游

#        '''

#        # self = obj

#        # Animal.__init__(人类对象,姓名,性别,年龄)

#        Animal.__init__(self,name,sex,age)

#        self.hobby = hobby

#

#

# class Dog(Animal):

#     pass

#

#

# class Cat(Animal):

#     pass

# obj = Human('驴友')

# obj2 = Human('抽烟')

# print(obj.__dict__)

# obj = Human('李业','男',18,'旅游')

# print(obj.__dict__)

# def func(self):

#     self = 666

#     print(self)

#

# self = 3

# # func(self)

# func(666)

# def func1(a,b):

#     print(a,b)

#

#

# def func2(argv1,argv2,x):

#     func1(argv1,argv2)

#     print(x)

#

# func2(1,2,666)

方法二: 依赖于继承

class Animal:

    def __init__(self, name, sex, age):

        self.name = name

        self.age = age

        self.sex = sex

    def eat(self):

        print('动物都需要吃饭')

class Human(Animal):

    def __init__(self, name, sex, age, hobby):

       # Animal.__init__(self,name,sex,age)

       # super(Human,self).__init__(name, sex, age)  #完整的写法

        super().__init__(name,sex,age)  # 执行父类的__init__方法,重构父类方法.

        self.hobby = hobby

    def eat(self):

        print(f'{self.name}都需要吃饭')

# class Dog(Animal):

#     pass

#

#

# class Cat(Animal):

#     pass

#

obj = Human('李业','男',18,'旅游')

obj.eat()

# print(obj.__dict__)
单继承练习题
# 1

class Base:

    def __init__(self, num):

        self.num = num

    def func1(self):

        print(self.num)

class Foo(Base):

    pass

obj = Foo(123)

obj.func1()

# 123

# 2

class Base:

    def __init__(self, num):

        self.num = num

    def func1(self):

        print(self.num)

class Foo(Base):

    def func1(self):

        print("Foo. func1", self.num)

obj = Foo(123)

obj.func1()

# Foo.func1 123

# 4

class Base:

    def __init__(self, num):

        self.num = num

    def func1(self):

        print(self.num)

        self.func2()

    def func2(self):

        print("Base.func2")

class Foo(Base):

    def func2(self):

    print("Foo.func2")

obj = Foo(123)

obj.func1()

# 123

# Foo.func2

# 再来

class Base:

    def __init__(self, num):

        self.num = num

    def func1(self):

        print(self.num)

        self.func2()

    def func2(self):

        print(111, self.num)

class Foo(Base):

    def func2(self):

        print(222, self.num)

lst = [Base(1), Base(2), Foo(3)]

for obj in lst:

    obj.func2()

# 111 1

# 111 2

# 222 3

# 再来

class Base:

    def __init__(self, num):

        self.num = num

    def func1(self):

        print(self.num)

        self.func2()

    def func2(self):

        print(111, self.num)

class Foo(Base):

    def func2(self):

        print(222, self.num)

lst = [Base(1), Base(2), Foo(3)]

for obj in lst:

 obj.func1()

# 1

# 111 1

# 2

# 111 2

# 3

# 222 3

多继承

引导

class ShenXian:

    def fly(self):

        print("神仙都会飞")

    def walk(self):

        print("神仙都会走路")

class Monkey:

    def climb(self):

        print("猴子都会爬树")

    def walk(self):

        print("猴子会走路")

class SunWuKong(ShenXian, Monkey):

    pass

sun = SunWuKong()

sun.fly()

sun.climb()

sun.walk()

python 类分为两种：

python2x：

python2.2之前，都是经典类

python2.2之后，经典类与新式类共存

python3x：

全部都是新式类

经典类

不继承object类，深度优先原则

深度优先原则:从左至右，深度优先

新式类

继承object类，mro（C3）算法

mro算法

class O:

    pass

class D(O):

    pass

class E(O):

    pass

class F(O):

    pass

class B(D,E):

    pass

class C(E,F):

    pass

class A(B,C):

    pass

obj = A()

print(obj.name)

# mro(Child(Base1，Base2)) = [ Child ] + merge( mro(Base1), mro(Base2), [ Base1, Base2] )

# mro(A(B,C)) = [A] + merge(mro(B),mro(C),[B,C])

"""

mro(A(B,C)) = [A] + merge(mro(B),mro(C),[B,C])

mro(B) = mro(B(D,E)) = [B] + merge(mro(D),mro(E),[D,E])

mro(B) = mro(B(D,E)) = [B] + merge([D,O],[E,O],[D,E])

mro(B) = mro(B(D,E)) = [B,D] + merge([O],[E,O],[E])

mro(B) = mro(B(D,E)) = [B,D,E] + merge([O],[O])

mro(B) = mro(B(D,E)) = [B,D,E,O]

mro(C) = mro(C(E,F)) = [C] + merge(mro(E),mro(F),[E,F])

mro(C) = mro(C(E,F)) = [C] + merge([E,O],[F,O],[E,F])

mro(C) = mro(C(E,F)) = [C,E] + merge([O],[F,O],[F])

mro(C) = mro(C(E,F)) = [C,E,F] + merge([O],[O])

mro(C) = mro(C(E,F)) = [C,E,F,O]

mro(A(B,C)) = [A] + merge([B,D,E,O],[C,E,F,O],[B,C])

mro(A(B,C)) = [A,B] + merge([D,E,O],[C,E,F,O],[C])

mro(A(B,C)) = [A,B,D] + merge([E,O],[C,E,F,O],[C])

mro(A(B,C)) = [A,B,D,C] + merge([E,O],[E,F,O])

mro(A(B,C)) = [A,B,D,C,E] + merge([O],[F,O])

mro(A(B,C)) = [A,B,D,C,E,F] + merge([O],[O])

mro(A(B,C)) = [A,B,D,C,E,F,O]

"""

print(A.mro())

# [<class '__main__.A'>, <class '__main__.B'>, <class '__main__.D'>, <class '__main__.C'>, <class '__main__.E'>, <class '__main__.F'>, <class '__main__.O'>, <class 'object'>]

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