Python笔记（十三）：类的继承

81 阅读 0 评论 54 点赞

我是靠谱客的博主帅气店员，最近开发中收集的这篇文章主要介绍Python笔记（十三）：类的继承，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

类有经典类和新式类，经典类即class people：新式类即class people(object):
新式类比经典类多了一些新的用法，比如在多继承的时候
- 在多继承时，如果继承的几个类都有构造函数，则按顺序只走第一个的构造函数
- Python2中，经典类按深度优先继承，新式类按广度优先继承
- Python3中，经典类和新式类都是广度优先。

- 继承
  - 重构父类方法
  - 子类中增加属性
  - 多继承
  - 继承示例：学校、讲师、学生

继承

可以直接继承父类的属性，减少了代码书写量

class people:
def __init__(self,name,age):
self.name = name
self.age = age
def eat(self):
print("%s is eating..." % self.name)
def talk(self):
print("%s is talking..." % self.name)
def sleep(self):
print("%s is sleeping..." % self.name)
class man(people):
pass

其中people为父类，man为子类
man完全继承了people中定义的姓名和年龄变量，以及后面的方法；

m1 = man("Evan",22)
m1.eat()
>> Evan is eating...

重构父类方法

可以在继承父类方法的基础上，再增加新功能；

class man(people):
def run(self):
print("%s is running..." % self.name)
def sleep(self):
people.sleep(self)
print("man is sleeping")
m1 = man("Evan",22)
m1.sleep()
>> Evan is sleeping...
>> man is sleeping

重构了父类中的方法，先调用了父类的方法，然后再执行子类的方法，这样两个结果都能得到。

如果子类中定义的方法和父类的重复了，则会执行子类的方法，将父类的覆盖了。

子类中增加属性

方法一：

class man(people):
def __init__(self,name,age,money):
people.__init__(self,name,age)
self.money = money
print("%s 出生自带 %s 钱" %(self.name,self.money))

再次调用父类的构造函数，然后在单独写要增加的属性。

方法二：

class man(people):
def __init__(self,name,age,money):
super(man,self).__init__(name,age)
self.money = money
print("%s 出生自带 %s 钱" %(self.name,self.money))

这种方法的好处在于：
1、如果父类改名字了，不用再进到每个子类中修改。
2、如果是继承多个父类，不用每个父类单独写一句调用构造函数。

多继承

经典类和新式类
定义的类，后面什么也不加就是经典类，加上object即为新式类；
新式类比经典类多了一些升级用法

比如：在子类中增加属性的方法二所用的super即新式类中的用法。

新式类的多继承：

class people(object):
def __init__(self,name,age):
self.name = name
self.age = age
def eat(self):
print("%s is eating..." % self.name)
def talk(self):
print("%s is talking..." % self.name)
def sleep(self):
print("%s is sleeping..." % self.name)
class relation(object):
def make_friends(self,obj):
print("%s is making friends with %s" % (self.name,obj.name))
class man(people,relation):
def __init__(self,name,age,money):
super(man,self).__init__(name,age)
self.money = money
print("%s 出生自带 %s 元钱" %(self.name,self.money))
class woman(people,relation):
def get_birth(self):
print("%s has borned a baby..." % self.name)
m1 = man("Evan",22,10)
w1 = woman("HanMM",20)
m1.make_friends(w1)
>> Evan 出生自带 10 元钱
>> Evan is making friends with HanMM

relation并没有写构造函数，为什么可以直接传参数？
因为在people中已经定义了这些属性，这些名字已经有了
在上述例子中，relation类中传入的参数obj其实就是输入的w1实例对象

继承示例：学校、讲师、学生

程序：

class School(object):
def __init__(self,name,addr):
self.name = name
self.addr = addr
self.students = []
self.staffs = []
def enroll(self,stu_obj):
print("为学员%s 办理注册手续" %stu_obj.name)
self.students.append(stu_obj)
def hire(self,staff_obj):
self.staffs.append(staff_obj)
print("雇佣新员工%s" % staff_obj.name)
class SchoolMember(object):
def __init__(self,name,age,sex):
self.name = name
self.age = age
self.sex = sex
def tell(self):
pass
class Teacher(SchoolMember):
def __init__(self,name,age,sex,salary,course):
super(Teacher,self).__init__(name,age,sex)
self.salary = salary
self.course = course
def tell(self):
print('''
------ info of Teacher:%s ------
Name:%s
Age:%s
Sex:%s
Salary:%s
Course:%s
'''%(self.name,self.name,self.age,self.sex,self.salary,self.course))
def teach(self):
print("%s is teaching course [%s]" %(self.name,self.course))
class Student(SchoolMember):
def __init__(self,name,age,sex,stu_id,grade):
super(Student,self).__init__(name,age,sex)
self.stu_id = stu_id
self.grade = grade
def tell(self):
print('''
------ info of Student:%s ------
Name:%s
Age:%s
Sex:%s
Stu_id:%s
Grade:%s
''' %(self.name,self.name,self.age,self.sex,self.stu_id,self.grade))
def pay_tuition(self,amount):
print("%s has paid tution for $%s" %(self.name,amount))
school = School("东方高中","洛阳")
t1 = Teacher("Lina",48,"female",20000,"Python")
t2 = Teacher("Tony",56,"male",8000,"Linux")
s1 = Student("Evan",22,"male",1301,"Python")
s2 = Student("Alan",24,"male",1302,"Linux")
t1.tell()
s1.tell()
school.hire(t1)
school.enroll(s1)
school.enroll(s2)
print(school.students)
print(school.staffs)
school.staffs[0].teach()
for stu in school.students:
stu.pay_tuition(5000)

SchoolMember()暂时没写什么，但如果以后再添加一些东西，比如将所有学校成员再添加一种属性，就方便了

程序运行结果：


------ info of Teacher:Lina ------
Name:Lina
Age:48
Sex:female
Salary:20000
Course:Python
------ info of Student:Evan ------
Name:Evan
Age:22
Sex:male
Stu_id:1301
Grade:Python
雇佣新员工Lina
为学员Evan 办理注册手续
为学员Alan 办理注册手续
[<__main__.Student object at 0x00000000028BA278>, <__main__.Student object at 0x00000000028BA2B0>]
[<__main__.Teacher object at 0x00000000028BA208>]
Lina is teaching course [Python]
Evan has paid tution for $5000
Alan has paid tution for $5000