day23——继承

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'>]