python类继承和组合

在python3中所有类默认继承object,凡是继承了object的类都成为新式类，以及该子类的子类Python3中所有的类都是新式类，没有集成object类的子类成为经典类(在Python2中没有集成object的类以及它的子类都是经典类

继承式用来创建新的类的一种方式，好处是减少重复代码

class People:
    def __init__(self,name,age):
        self.name=name
        self.age=age
    def walking(self):
        print(‘%s is walking ‘ %self.name)
    def talking(self):
        print(‘%s is talking ‘%self.name)

class Teacher(People):
    pass
class Student(People):
    pass

t1=Teacher(‘egon‘,18)
print(t1.name,t1.age)
t1.walking()
t1.talking()
s1=Student(‘xiaobai‘,22)
print(s1.name,s1.age)
s1.talking()
s1.walking()
执行结果
egon 18
egon is walking
egon is talking
xiaobai 22
xiaobai is talking
xiaobai is walking 

class People:
    def __init__(self,name,age,sex):
        self.name=name
        self.age=age
        self.sex=sex
    def walking(self):
        print(‘%s is walking ‘ %self.name)
    def talking(self):
        print(‘%s is talking ‘%self.name)

class Teacher(People):
    def __init__(self,name,age,sex,level,salary):
        People.__init__(name,age,sex)
        self.level=level
        self.salary=salary
    def teaching(self):
        People.talking(self)
        print(‘%s is teaching‘%self.name)
class Student(People):
    def __init__(self,name,age,sex,group):
        People.__init__(name,age,sex)
        self.group=group
    def studying(self):
        People.talking(self)
        print(‘%s is studying‘%self.name)

组合

class Date:
    def __init__(self,year,mon,day):
        self.year=year
        self.mon=mon
        self.day=day
    def tell_birth(self):
        print(‘出生于<%s>年 <%s>月 <%s>日‘%(self.year,self.mon,self.day))

class Teacher:
    def __init__(self,name,age,sex,year,month,day):
        self.name=name
        self.age=age
        self.sex=sex
        self.birth=Date(year,month,day)
    def teaching(self):
        print(‘%s is teaching‘%self.name)
class Student:
    def __init__(self,name,age,sex,year,mon,day):
        self.name=name
        self.age=age
        self.sex=sex
        self.birth=Date(year,mon,day)
    def studying(self):
        print(‘%s is studying‘%self.name)

xiaobai=Student(‘xiaobai‘,22,‘male‘,‘1995‘,‘3‘,‘16‘)
xiaobai.birth.tell_birth()
执行结果
出生于<1995>年 <3>月 <16>日

继承和组合

class People:
    def __init__(self,name,age,sex,year,mon,day):
        self.name=name
        self.age=age
        self.sex=sex
        self.birth=Date(year,mon,day)
    def walking(self):
        print(‘%s is walking ‘ %self.name)
    def talking(self):
        print(‘%s is talking ‘%self.name)

class Date:
    def __init__(self,year,mon,day):
        self.year=year
        self.mon=mon
        self.day=day
    def tell_birth(self):
        print(‘出生于<%s>年 <%s>月 <%s>日‘%(self.year,self.mon,self.day))

class Teacher(People):
    def __init__(self,name,age,sex,level,salary,year,mon,day):
        People.__init__(self,name,age,sex,year,mon,day)
        self.level=level
        self.salary=salary
    def teaching(self):
        People.talking(self)
        print(‘%s is teaching‘%self.name)
class Student(People):
    def __init__(self,name,age,sex,year,mon,day,group):
        People.__init__(self,name,age,sex,year,mon,day)
        self.group=group
    def studying(self):
        People.talking(self)
        print(‘%s is studying‘%self.name)

父类要限制
1、子类必须有父类的方法
2、子类实现的方法必须跟父类的方法的名字一样

import abc

class File(metaclass=abc.ABCMeta):
    @abc.abstractclassmethod
    def read(self):
        pass
    @abc.abstractclassmethod
    def write(self):
        pass