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'>]
