我在b站学python之基础学习十五：继承
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一、体验继承
#定义父类
class A(object):
def _init_(self):
self.num = 1
def info_print(self):
print(self.num)
#定义子类，继承父类
class B(A):
pass
#创建对象，验证结论
result = B()
result.info_print()
注意：在python中，所有类默认继承object类，object类是顶级类或者基类，其他子类叫派生类。
二、单继承
例
#师傅类，属性和方法
class Master(object):
def _init_(self):
self.kongfu = '[师父的]'
def make_cake(self):
print(f'{self.kongfu}')
#定义徒弟类，继承师傅类
class Prentice(Master):
pass
#徒弟类创建对象，调用实例属性和方法
daqiu = Prentice()
print(daqiu.kongfu)
daqiu.make_cake()
三、多继承
例
class Master(object):
def _init_(self):
self.kongfu = '[师父的]'
def make_cake(self):
print(f'{self.kongfu}')
#创建学校类
class School(object):
def _init_(self):
self.kongfu = '[学校的]'
def make_cake(self):
print(f'{self.kongfu}')
class Prentice(School,Master):
pass
daqiu = Prentice()
print(daqiu.kongfu)
daqiu.make_cake()
注意：当一个类有多个父类的时候，默认使用第一个父类的同名属性和方法。
四、子类重写父类同名方法和属性
例、
class Master(object):
def _init_(self):
self.kongfu = '[师父的]'
def make_cake(self):
print(f'{self.kongfu}')
class School(object):
def _init_(self):
self.kongfu = '[学校的]'
def make_cake(self):
print(f'{self.kongfu}')
class Prentice(School,Master):
def _init_(self):
self.kongfu = '我的'
def make_cake(self):
print(f'{self.kongfu}')
daqiu = Prentice()
print(daqiu.kongfu)
daqiu.make_cake()
注意：如果子类和父类拥有同名属性和方法，子类创建对象调用属性和方法的时候，调用到的是子类里边的同名属性和方法
五、快速查看类的继承关系
语法：类名.mro
例：
上边代码运行：print（Prentice.mro）
结果：
六、子类调用父类的同名方法和属性（方法一，方法二见下）
例：
class Master(object):
def _init_(self):
self.kongfu = '[师父的]'
def make_cake(self):
print(f'{self.kongfu}')
class School(object):
def _init_(self):
self.kongfu = '[学校的]'
def make_cake(self):
print(f'{self.kongfu}')
class Prentice(School,Master):
def _init_(self):
self.kongfu = '我的'
def make_cake(self):
self._init_() #加自己初始化原因：如果不加，属性值是上一次调用的init内的属性值
print(f'{self.kongfu}')
#子类调用父类的同名方法和属性，把父类的同名属性和方法再次封装
def make_master_cake(self):
Master._init_(self) #再次调用初始化的原因：想要调用弗雷德同名方法和属性，属性在init初始化位置，所以需要再次调用
Master.make_cake(self)
def make_school_cake(self):
School._init_(self)
School.make_cake(self)
daqiu = Prentice()
daqiu.make_cake()
daqiu.make_master_cake()
daqiu.make_school_cake()
七、多层继承
例：
class Master(object):
def _init_(self):
self.kongfu = '[师父的]'
def make_cake(self):
print(f'{self.kongfu}')
class School(object):
def _init_(self):
self.kongfu = '[学校的]'
def make_cake(self):
print(f'{self.kongfu}')
class Prentice(School,Master):
def _init_(self):
self.kongfu = '我的'
def make_cake(self):
self._init_()
print(f'{self.kongfu}')
def make_master_cake(self):
Master._init_(self)
Master.make_cake(self)
def make_school_cake(self):
School._init_(self)
School.make_cake(self)
#徒孙类
class Tusun(Prentice):
pass
xiaoqiu = Tusun()
xiaoqiu.make_cake()
xiaoqiu.make_school_cake()
xiaoqiu.make_master_cake()
八、super()调用父类方法（方法二）
例：
1、super()有参数方法
class Master(object):
def _init_(self):
self.kongfu = '[师父的]'
def make_cake(self):
print(f'{self.kongfu}')
class School(Master):
def _init_(self):
self.kongfu = '[学校的]'
def make_cake(self):
print(f'{self.kongfu}')
#super（）带参数写法
super(School,self)._init_()
super(School,self).make_cake()
class Prentice(School:
def _init_(self):
self.kongfu = '我的'
def make_cake(self):
self._init_()
print(f'{self.kongfu}')
def make_master_cake(self):
Master._init_(self)
Master.make_cake(self)
def make_school_cake(self):
School._init_(self)
School.make_cake(self)
#方法一：super（当前类名，self）.函数（）
def make_old_cake(self):
super(Prentice,self)._init_()
super(Prentice,self).make_cake()
daqiu = Prentice()
daqiu.make_old_cake()
2、super()无参数方法
class Master(object):
def _init_(self):
self.kongfu = '[师父的]'
def make_cake(self):
print(f'{self.kongfu}')
class School(Master):
def _init_(self):
self.kongfu = '[学校的]'
def make_cake(self):
print(f'{self.kongfu}')
#super（）无参数写法
super()._init_()
super().make_cake()
class Prentice(School:
def _init_(self):
self.kongfu = '我的'
def make_cake(self):
self._init_()
print(f'{self.kongfu}')
def make_master_cake(self):
Master._init_(self)
Master.make_cake(self)
def make_school_cake(self):
School._init_(self)
School.make_cake(self)
#方法二：super（）.函数（）
def make_old_cake(self):
super()._init_()
super().make_cake()
daqiu = Prentice()
daqiu.make_old_cake()
九、私有权限
即设置某个实例属性或实例方法不继承给子类
1、设置私有权限方法：在属性名和方法名前加两个下划线。
例：
class Master(object):
def _init_(self):
self.kongfu = '[师父的]'
def make_cake(self):
print(f'{self.kongfu}')
class School(object):
def _init_(self):
self.kongfu = '[学校的]'
def make_cake(self):
print(f'{self.kongfu}')
class Prentice(School,Master):
def _init_(self):
self.kongfu = '我的'
#创建私有属性self.__money
self.__money() = 20
#定义私有方法
def __info_print(self):
print('私有方法')
def make_cake(self):
self._init_()
print(f'{self.kongfu}')
def make_master_cake(self):
Master._init_(self)
Master.make_cake(self)
def make_school_cake(self):
School._init_(self)
School.make_cake(self)
class Tusun(Prentice):
pass
xiaoqiu = Tusun()
#以上代码分别执行下列代码 都会报错
print(xiaoqiu.money)
print(xiaoqiu.__money)
xiaoqiu.__info_print()
2、获取和修改私有属性值
一般定义函数名get_xx用来获取私有属性，定义set_xx用来修改私有属性值。
例：
class Master(object):
def _init_(self):
self.kongfu = '[师父的]'
def make_cake(self):
print(f'{self.kongfu}')
class School(object):
def _init_(self):
self.kongfu = '[学校的]'
def make_cake(self):
print(f'{self.kongfu}')
class Prentice(School,Master):
def _init_(self):
self.kongfu = '我的'
self.__money = 20
#定义函数，获取私有属性值
def get_money(self):
return self.__money
#定义函数修改私有属性值
def set_money(self):
self.__money = 50
def make_cake(self):
self._init_()
print(f'{self.kongfu}')
def make_master_cake(self):
Master._init_(self)
Master.make_cake(self)
def make_school_cake(self):
School._init_(self)
School.make_cake(self)
#徒孙类
class Tusun(Prentice):
pass
xiaoqiu = Tusun()
print(xiaoqiu.get_money()) #获取私有属性money的值
xiaoqiu.set_money() #修改私有属性money的值
print(xiaoqiu.get_money())
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