Python⾯向对象的继承指的是多个类之间的所属关系，即⼦类默认继承⽗类的所有属性和⽅法，具体如下：
# ⽗类A
class A(object):
def __init__(self):
self.num = 1
def info_print(self):
print(self.num)
# ⼦类B
class B(A):
pass
result = B()
result.info_print() # 1
在Python中，所有类默认继承object类，object类是顶级类或基类；其他⼦类叫做派⽣类。
单继承
# 1. 师⽗类
class Master(object):
def __init__(self):
self.kongfu = '[古法煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
# 2. 徒弟类
class Prentice(Master):
pass
# 3. 创建对象daqiu
daqiu = Prentice()
# 4. 对象访问实例属性
print(daqiu.kongfu)
# 5. 对象调⽤实例⽅法
daqiu.make_cake()
多继承
所谓多继承意思就是⼀个类同时继承了多个⽗类。
class Master(object):
def __init__(self):
self.kongfu = '[古法煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
# 创建学校类
class School(object):
def __init__(self):
self.kongfu = '[学校煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
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。
⼦类重写⽗类同名⽅法和属性
class Master(object):
def __init__(self):
self.kongfu = '[古法煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
# 创建学校类
class School(object):
def __init__(self):
self.kongfu = '[学校煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
# 独创配⽅
class Prentice(School, Master):
def __init__(self):
self.kongfu = '[独创煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
daqiu = Prentice()
print(daqiu.kongfu)
daqiu.make_cake()
print(Prentice.__mro__)
⼦类和⽗类具有同名属性和⽅法，默认使⽤⼦类的同名属性和⽅法。
⼦类调⽤⽗类的同名⽅法和属性
class Master(object):
def __init__(self):
self.kongfu = '[古法煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
# 创建学校类
class School(object):
def __init__(self):
self.kongfu = '[学校煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
class Prentice(School, Master):
def __init__(self):
self.kongfu = '[独创煎饼果⼦配⽅]'
def make_cake(self):
# 如果是先调⽤了⽗类的属性和⽅法，⽗类属性会覆盖⼦类属性，故在调⽤属性前，先调⽤
⾃⼰⼦类的初始化
self.__init__()
print(f'运⽤{self.kongfu}制作煎饼果⼦')
# 调⽤⽗类⽅法，但是为保证调⽤到的也是⽗类的属性，必须在调⽤⽅法前调⽤⽗类的初始化
def make_master_cake(self):
Master.__init__(self)
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()
daqiu.make_cake()
多层继承
class Master(object):
def __init__(self):
self.kongfu = '[古法煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
# 创建学校类
class School(object):
def __init__(self):
self.kongfu = '[学校煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
class Prentice(School, Master):
def __init__(self):
self.kongfu = '[独创煎饼果⼦配⽅]'
def make_cake(self):
self.__init__()
print(f'运⽤{self.kongfu}制作煎饼果⼦')
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()
super()调⽤⽗类⽅法
class Master(object):
def __init__(self):
self.kongfu = '[古法煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
# 创建学校类
class School(object):
def __init__(self):
self.kongfu = '[学校煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
# ⽅法2.1
# super(School, self).__init__()
# super(School, self).make_cake()
# ⽅法2.2
super().__init__()
super().make_cake()
class Prentice(School, Master):
def __init__(self):
self.kongfu = '[独创煎饼果⼦配⽅]'
def make_cake(self):
self.__init__()
print(f'运⽤{self.kongfu}制作煎饼果⼦')
def make_master_cake(self):
Master.__init__(self)
Master.make_cake(self)
def make_school_cake(self):
School.__init__(self)
School.make_cake(self)
# ⼀次性调⽤⽗类的同名属性和⽅法
def make_old_cake(self):
# ⽅法⼀：代码冗余；⽗类类名如果变化，这⾥代码需要频繁修改
# Master.__init__(self)
# Master.make_cake(self)
# School.__init__(self)
# School.make_cake(self)
# ⽅法⼆: super()
# ⽅法2.1 super(当前类名, self).函数()
# super(Prentice, self).__init__()
# super(Prentice, self).make_cake()
# ⽅法2.2 super().函数()
super().__init__()
super().make_cake()
daqiu = Prentice()
daqiu.make_old_cake()
注意：使⽤
super()可以⾃动查找⽗类。调⽤顺序遵循__mro__类属性的顺序。⽐较适合单继承使⽤。
私有权限
定义私有属性和⽅法
在Python中，可以为实例属性和⽅法设置私有权限，即设置某个实例属性或实例⽅法不继承给⼦类。
设置私有权限的⽅法：在属性名和⽅法名 前⾯ 加上两个下划线 __。
class Master(object):
def __init__(self):
self.kongfu = '[古法煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
# 创建学校类
class School(object):
def __init__(self):
self.kongfu = '[学校煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
class Prentice(School, Master):
def __init__(self):
self.kongfu = '[独创煎饼果⼦配⽅]'
# 定义私有属性
self.__money = 2000000
# 定义私有⽅法
def __info_print(self):
print(self.kongfu)
print(self.__money)
def make_cake(self):
self.__init__()
print(f'运⽤{self.kongfu}制作煎饼果⼦')
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
daqiu = Prentice()
# 对象不能访问私有属性和私有⽅法
# print(daqiu.__money)
# daqiu.__info_print()
xiaoqiu = Tusun()
# ⼦类⽆法继承⽗类的私有属性和私有⽅法
# print(xiaoqiu.__money) # ⽆法访问实例属性__money
# xiaoqiu.__info_print()
注意：私有属性和私有⽅法只能在类⾥⾯访问和修改。
获取和修改私有属性值
在Python中，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。
class Master(object):
def __init__(self):
self.kongfu = '[古法煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
# 创建学校类
class School(object):
def __init__(self):
self.kongfu = '[学校煎饼果⼦配⽅]'
def make_cake(self):
print(f'运⽤{self.kongfu}制作煎饼果⼦')
class Prentice(School, Master):
def __init__(self):
self.kongfu = '[独创煎饼果⼦配⽅]'
self.__money = 2000000
# 获取私有属性
def get_money(self):
return self.__money
# 修改私有属性
def set_money(self):
self.__money = 500
def __info_print(self):
print(self.kongfu)
print(self.__money)
def make_cake(self):
self.__init__()
print(f'运⽤{self.kongfu}制作煎饼果⼦')
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
daqiu = Prentice()
xiaoqiu = Tusun()
# 调⽤get_money函数获取私有属性money的值
print(xiaoqiu.get_money())
# 调⽤set_money函数修改私有属性money的值
xiaoqiu.set_money()
print(xiaoqiu.get_money())
