python中类的应用（继承与派生）

继承与派生

什么是继承

继承是一种新建类的方式，新建的类称为子类，子类会遗传父类的属性，可以减少代码冗余，
在python中，子类（派生类）可以继承一个或者多个父类（基类，超类）

例如：

class Parent1:
    pass
class Parent2(object):
    pass
class Sub1(Parent1):
    pass
class Sub2(Parent1,Parent2):
    pass

print(Sub1.__bases__)    #查看类的父类
print(Sub2.__bases__)

print(Parent1.__bases__)  #在python3新建的类，默认都有一个父类（object）  #在python2中，默认是没有父类，可以添加（object）为父类
print(Parent2.__bases__)

python中类的分类

在python2中：

1、经典类，指的就是没有继承object类的类，以及该类的子类

2、新式类，指的就是继承object类的类，以及该类的子类

在python3中：

统一都是新式类

例如：

class OldboyPeople:
    school='oldboy'

    def __init__(self,name,age,sex):
        self.name=name
        self.age=age
        self.sex=sex
    def tell_info(self):
        print('<名字：%s 年龄：%s 性别：%s>' %(self.name,self.age,self.sex))
class OldboyStudent(OldboyPeople):
    def learn(self):
        print('%s is learning' %self.name)
    def tell_info(self):
        print('我是学生：',end='')
class OldboyTreacher(OldboyPeople):
    def teach(self):
        print('%s is teaching' %self.name)
    def tell_info(self):
        print('我是老师：',end='')
        print('<名字：%s 年龄：%s 性别：%s>' %(self.name,self.age,self.sex))
stu1=OldboyStudent('lqx','19','male')
teaching=OldboyTreacher('egon','23','female')

print(stu1.__dict__)
print(stu1.school)
# print(stu1.x)  #查找顺序，对象->子类->父类 没有就抛异常
print(teaching.__dict__)

# 如果子类有这个函数，就不会去父类去找
stu1.tell_info()
teaching.tell_info()

#属性查找：
class Foo:
    def f1(self):
        print('foo.f1')
    def f2(self):       #self应该为Bar初始化的obj对象
        print('foo.f2')
        self.f1()   #Bar初始化的obj.f1()
class Bar(Foo):
    def f1(self):
        print('bar.f1')
obj=Bar()
print(obj.__dict__)
obj.f2()  #先在bar类中查找，如果没有就会去父类查找，

# >>>foo.f2
# bar.f1

子类重用父类的方法

指名道姓的使用

#子类指名道姓使用父类属性
#实现学生还有课程、学号
class OldboyPeople:
    school='oldboy'

    def __init__(self,name,age,sex):
        self.name=name
        self.age=age
        self.sex=sex
    def tell_info(self):
        print('<名字：%s 年龄：%s 性别：%s 课程：%s 学号：%s>' %(self.name,self.age,self.sex,self.coutse,self.stu_id))
class OldboyStudent(OldboyPeople):
    def __init__(self,name,age,sex,coutse,stu_id):
        OldboyPeople.__init__(self,name,age,sex)   #子类指名道姓使用父类属性
        self.coutse=coutse
        self.stu_id=stu_id
    def learn(self):
        print('%s is learning' %self.name)
    def tell_info(self):
        print('我是学生：',end='')
        OldboyPeople.tell_info(self)    #子类指名道姓使用父类属性


stu1=OldboyStudent('lqx','19','male','python','123')
stu1.tell_info()

使用super来调用父类的方法

1、之前使用指名道姓的引用另一个类，或者父类的方法。

2、现在使用super(本类名.self).方法 的方式调用父类的方法

3、这种方法只能调用父类的方法

class OldboyPeople:
    school = 'Oldboy'
    def __init__(self, name, age, sex):
        self.name = name
        self.age = age
        self.sex = sex

    def tell_info(self):
        print('<名字:%s 年龄:%s 性别:%s>' %(self.name,self.age,self.sex))

class OldboyStudent(OldboyPeople):
    def __init__(self,name,age,sex,course):
        # OldboyPeople.__init__(self,name,age,sex)
        super(OldboyStudent,self).__init__(name,age,sex)
        self.course=course

    def tell_info(self):
        print('我是学生: ',end='')
        # OldboyPeople.tell_info(self)
        super(OldboyStudent,self).tell_info()

stu1=OldboyStudent('lqx','12','male','python')
print(stu1.name,stu1.age,stu1.sex,stu1.course)
stu1.tell_info()

super方法

class Foo:
    # def f2(self):
        # print('>>>>2')
    def f1(self):
        print('foo.f1')
        Foo.f2(123)
class Bar:
    def f2(self):
        print('bar f2')
class Sub(Bar,Foo):
    pass

s=Sub()
print(Sub.mro())  #[, , , ]

s.f1()  #说明严格按照mro()中的查找顺序来查找

#查找顺序，Sub->Bar->Foo

组合的使用

#学生有年龄名字，性别，学号，还有生日，使用组合添加出生日
#组合区别于继承，什么有什么的一种关系
class OldboyPeople:
    school='oldboy'

    def __init__(self,name,age,sex):
        self.name=name
        self.age=age
        self.sex=sex
    def tell_info(self):
        print('<名字：%s 年龄：%s 性别：%s 课程：%s 学号：%s>' %(self.name,self.age,self.sex,self.coutse,self.stu_id))
class OldboyStudent(OldboyPeople):
    def __init__(self,name,age,sex,coutse,stu_id,date_obj):
        OldboyPeople.__init__(self,name,age,sex)
        self.coutse=coutse
        self.stu_id=stu_id
        self.birth=date_obj   #3、把date_obj添加到self这个对象中

    def learn(self):
        print('%s is learning' %self.name)
    def tell_info(self):
        print('我是学生：',end='')
        OldboyPeople.tell_info(self)

class OldboyTreacher(OldboyPeople):
    def __init__(self,name,age,sex,level,salary):
        OldboyPeople.__init__(self, name, age, sex)
        self.level = level
        self.salary = salary
    def teach(self):
        print('%s is teaching' %self.name)
    def tell_info(self):
        print('我是老师：',end='')
        print('<名字：%s 年龄：%s 性别：%s>' %(self.name,self.age,self.sex))

class Date:
    def __init__(self,year,mon,day):
        self.year = year
        self.mon = mon
        self.day = day

    def tell_birth(self):
        print('出生日期是：%s-%s-%s' % (self.year, self.mon, self.day))

date_obj=Date('1921',21,23)   #1、先初始化生日得到一个对象
stu1=OldboyStudent('lqx','19','male','python','12',date_obj)  #2、初始化学生类，把初始化生日的对象带入一起初始化
stu1.birth.tell_birth()   #4、就可以调用对象stu1中birth的属性

teacher1=OldboyTreacher('www','123','female',10,12)
date_obj2=Date(1990,2,18)
teacher1.brith=date_obj2


# 添加一个生日，把生日任何人都有生日，把生日放到父类中，初始化的时候就会有生日
class OldboyPeople:
    school='oldboy'

    def __init__(self,name,age,sex,date_obj):
        self.name=name
        self.age=age
        self.sex=sex
        self.birth=date_obj
    def tell_info(self):
        print('<名字：%s 年龄：%s 性别：%s >' %(self.name,self.age,self.sex))

class OldboyStudent(OldboyPeople):
    def __init__(self,name,age,sex,coutse,stu_id,date_obj):
        OldboyPeople.__init__(self,name,age,sex,date_obj)
        self.coutse=coutse
        self.stu_id=stu_id


    def learn(self):
        print('%s is learning' %self.name)
    def tell_info(self):
        print('我是学生：',end='')
        OldboyPeople.tell_info(self)
        print('课程：%s 学号：%s' %(self.coutse,self.stu_id))

class OldboyTreacher(OldboyPeople):
    def __init__(self,name,age,sex,level,salary,date_obj):
        OldboyPeople.__init__(self, name, age, sex,date_obj)
        self.level = level
        self.salary = salary
    def teach(self):
        print('%s is teaching' %self.name)
    def tell_info(self):
        print('我是老师：',end='')
        print('<名字：%s 年龄：%s 性别：%s>' %(self.name,self.age,self.sex))

class Date:
    def __init__(self,year,mon,day):
        self.year = year
        self.mon = mon
        self.day = day
    def tell_birth(self):
        print('出生日期是：%s-%s-%s' % (self.year, self.mon, self.day))

class OldboySale(OldboyPeople):
    def __init__(self,name,age,sex,kpi,date_obj):
        OldboyPeople.__init__(self,name,age,sex,date_obj)
        self.kpi=kpi

    def tell_info(self):
        print('销售：%s',end='')
        OldboyPeople.tell_info(self)

date_obj=Date('1921',21,23)   
stu1=OldboyStudent('lqx','19','male','python','12',date_obj)  
stu1.birth.tell_birth()  

date_obj2=Date(1990,2,18)
teacher1=OldboyTreacher('www','123','female',10,12,date_obj2)
teacher1.birth.tell_birth()
print(teacher1.__dict__)

date_obj1=Date(1800,12,32)
sale1=OldboySale('mmp','12','female',7.1,date_obj1)
print(sale1.__dict__)
sale1.birth.tell_birth()



#学生选课，添加选择的课程，在初始化的时候初始化一个属性为list
class OldboyPeople:
    school='oldboy'

    def __init__(self,name,age,sex,date_obj):
        self.name=name
        self.age=age
        self.sex=sex
        self.birth=date_obj
    def tell_info(self):
        print('<名字：%s 年龄：%s 性别：%s >' %(self.name,self.age,self.sex),end='')

class OldboyStudent(OldboyPeople):
    def __init__(self,name,age,sex,date_obj,stu_id):
        OldboyPeople.__init__(self,name,age,sex,date_obj)
        self.coutse=[]
        self.stu_id=stu_id


    def learn(self):
        print('%s is learning' %self.name)
    def tell_info(self):
        print('我是学生：',end='')
        OldboyPeople.tell_info(self)
        print('学号：%s' %self.stu_id)

class OldboyTreacher(OldboyPeople):
    def __init__(self,name,age,sex,level,salary,date_obj):
        OldboyPeople.__init__(self, name, age, sex,date_obj)
        self.level = level
        self.salary = salary
        self.courses=[]
    def teach(self):
        print('%s is teaching' %self.name)
    def tell_info(self):
        print('我是老师：',end='')
        print('<名字：%s 年龄：%s 性别：%s>' %(self.name,self.age,self.sex))

class Date:
    def __init__(self,year,mon,day):
        self.year = year
        self.mon = mon
        self.day = day
    def tell_birth(self):
        print('出生日期是：%s-%s-%s' % (self.year, self.mon, self.day))

class OldboySale(OldboyPeople):
    def __init__(self,name,age,sex,kpi,date_obj):
        OldboyPeople.__init__(self,name,age,sex,date_obj)
        self.kpi=kpi

    def tell_info(self):
        print('销售：%s',end='')
        OldboyPeople.tell_info(self)


class Course:
    def __init__(self,name,price,period):
        self.name=name
        self.price=price
        self.period=period
    def tell_info(self):
        print('课程详细信息：（%s,%s,%s）' %(self.name,self.price,self.period))

Python=Course('python自动化',4000,'3mon')
Linux=Course('linux学习',2000,'3mon')

# date_obj=Date(1990,12,32)
# tearch1=OldboyTreacher('egon','19','male',100,3000,date_obj)
# tearch1.courses.append(Python)
# for course in tearch1.courses:
#     course.tell_info()

date_obj=Date(1994,21,12)
stu1=OldboyStudent('LQX',29,'male',date_obj,'1')
stu1.coutse.append(Linux)
stu1.coutse.append(Python)
stu1.tell_info()
for coutse in stu1.coutse:
    coutse.tell_info()

抽象类

主要使用abc模块，实现归一化，父类有的方法，子类必须有。

需要在父类的方法头部加上@abc.abstractclassmethod

例如：

class File(metaclass=abc.ABCMeta):
    @abc.abstractmethod 
    def read(self):   #必须要定义下面的方法，如果没有就不让实例化
        pass
    @abc.abstractmethod
    def write(self):
        pass
class Sata(File):
    def read(self):
        pass
    def write(self):
        pass
    def asb(self):
        print('adsf')
Fil=Sata()
Fil.asb()
print(Sata.mro())

继承的实现原理

1、继承顺序：

经典类：当类是经典类时，多继承情况下，在要查找属性不存在时，会按照深度优先的方式查找下去

新式类：当类是新式类时，多继承情况下，在要查询属性不存在时，会按照广度优先的方式查找下去

2、使用属性来查看继承的顺序：

print(类名.mro())

class A(object):
    # def test(self):
    #     print('from A')
    pass

class B(A):
    # def test(self):
    #     print('from B')
    pass

class C(A):
    # def test(self):
    #     print('from C')
    pass
class D(B):
    # def test(self):
    #     print('from D')
    pass

class E(C):
    # def test(self):
    #     print('from E')
    pass
class F(D,E):
    # def test(self):
    #     print('from F')
    pass

f1=F()
print(F.mro())