面向对象——继承

概念

面向对象编程 (OOP) 语言的一个主要功能就是“继承”。继承是指这样一种能力：它可以使用现有类的所有功能，并在无需重新编写原来的类的情况下对这些功能进行扩展。当同一个类的对象有共同的属性也有不同的属性时，我们就弄一个父类弄多个子类，子类继承父类的属性，且子类又有自己特有的属性。是面向对象（oop）的主要功能

被继承的类称为 “父类”或者“基类”

通过继承创建的新类称为“子类”或者“派生类”

继承概念的实现方式主要有2类：实现继承、接口继承。

1. 实现继承是指使用基类的属性和方法而无需额外编码的能力。
2. 接口继承是指仅使用属性和方法的名称、但是子类必须提供实现的能力(子类重构爹类方法)。

 子类继承父类方法如下例子：

说明：在子类名的括号中写入需要继承的类名（父类的类名）即可

class Person(object):
    def talk(self):
        print("people is taking....ll")


class blackpeople(Person):
    def walk(self):
        print("blackpeople in walking...")

p1 = blackpeople()
p1.talk()  #继承了父类，所以talk()方法可以被调用 
p1.walk() 
结果： 
people is taking....ll 
blackpeople in walking...

若父类里有构造函数含有参数，子类继承父类时应把参数传递进去，否则会报错

class Person(object):
    def __init__(self,name,age):
        self.name = name
        self.age = age
    def talk(self):
        print("people is taking....ll")


class blackpeople(Person):
    def walk(self):
        print("blackpeople in walking...")

p1 = blackpeople()
p1.talk()
p1.walk()

报错：
Traceback (most recent call last):
  File "E:/python_3.5/stu/继承模块.py", line 16, in <module>
    p1 = blackpeople()
TypeError: __init__() missing 2 required positional arguments: 'name' and 'age'

将参数传递进去

class Person(object):
    def __init__(self,name,age):
        self.name = name
        self.age = age
    def talk(self):
        print("people is taking....ll")


class blackpeople(Person):
    def walk(self):
        print("blackpeople in walking...")

p1 = blackpeople("HiHi",11)
p1.talk()
p1.walk()

若想要继承父类的构造函数，同时又要有自己的属性（功能），做法是先继承再构造

class People(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age
        self.height = "normal"

    def talk(self):
        print("People is talking...")


class BlackPelple(People):
    def __init__(self, name, age, sex):  # 定义时需要传入父类的属性名
        People.__init__(self, name, age)  # 继承父类的构造方法，也可以写成：super(BlackPerson,self).__init__(name,age)
        self.sex = sex  # 定义子类本身属性
        print(self.name, self.age, self.height)

    def walk(self):
        print("the people is walking...")

p = BlackPelple("wxq", 22 ,"女")  # 创建一个实例
print(p.sex)
p.talk()
p.walk()

结果：
wxq 22 normal
女
People is talking...
the people is walking...

练习 

类继承联系

#!/usr/bin/env python
# -*- coding:utf-8 -*-

class SchoolMember(object):
    """学校成员基类"""
    member = 0
    def __init__(self, name, age, sex):
        self.name = name
        self.age = age
        self.sex = sex

    def enrrol(self):
        print("just enrrol new school member")
        SchoolMember.member += 1

    def tell(self):
        print("------info:%s-----"%(self.name))
        for k, v in self.__dict__.items():
            print("	", k, v)

        print("------end------")

    def __del__(self):
        print("开除了...%s"%(self.name))
        SchoolMember.member -= 1


class Teacher(SchoolMember):
    """讲师类"""
    def __init__(self, name, age, sex, salary, course):
        SchoolMember.__init__(self, name, age, sex)
        self.salary = salary
        self.course = course

    def teaching(self):
        """讲课方法"""
        print("Teacher %s is teaching %s "%(self.name, self.course))

class Student(SchoolMember):
    """学生类"""
    def __init__(self, name, age, sex, tuition, course):
        SchoolMember.__init__(self, name, age, sex)
　　　　 # 或者
　　　　 # super(Student, self).__init__(name, age, sex)

        self.tuition = tuition
        self.course = course

    def pay_tuition(self, amount):
        print("student %s has just paied %s"%(self.name, amount))
        self.amount += amount

t1 = Teacher("Lily", 22, "女", 6666, "Python")
s1 = Student("A1", 12, "男", "PYS15", 1 )
s2 = Student("A2", 12, "男", "PYS14", 1 )
print(SchoolMember.member)
t1.tell()
s1.tell()
s2.tell()



结果：
0
------info:Lily-----
     salary 6666
     age 22
     sex 女
     course Python
     name Lily
------end------
------info:A1-----
     tuition PYS15
     age 12
     sex 男
     course 1
     name A1
------end------
------info:A2-----
     tuition PYS14
     age 12
     sex 男
     course 1
     name A2
------end------
开除了...Lily
开除了...A1
开除了...A2