python基础（八）：封装、继承、多态

面向对象

特征

封装、继承、多态

封装示例

1.析构函数

c++有相似概念，repr函数输出对象时不输出全部信息

class Book:
    count = 0
    #def __init__(self,title,price = 0.0,author=None,count = 0):
    ##构造函数
    def __init__(self, title, price=0.0, author=None):
        self.title = title
        self.price = price
        self.author = author
        Book.count += 1
    ##析构函数，删除对象使用
    def __del__(self):
        Book.count -= 1

    ##控制台上直接使用对象执行
    def __repr__(self):
        return ''.format(self.title,id(self))
    ##打印时执行
    def __str__(self):
        return '[BOOK{},PRICE{}]'.format(self.title,self.price)

    def print_info(self):
        print(self.title,self.price,self.author)

    def cls_method(cls):
        print('类函数')


    def static_method():
        print('静态函数，逻辑上与实例无关')

if __name__ == '__main__':
    book = Book('python base',price = 20,author = 'Tom')
    #Book.count += 1
    book2 = Book('Flask')
   # Book.count += 1
    book3 = Book('ASP.net')
    #Book.count += 1

    del(book3)

    print(Book.count)
    Book.cls_method(book)
    Book.static_method()

输出
2
类函数
静态函数，逻辑上与实例无关

2.过滤装饰器

property，setter，deleter

import datetime

class Student:

    def __init__(self,name,birthdate):
        self.name = name
        self.birthdate = birthdate

    @property
    ##属性,好处进一步过滤
    def age(self):
        return datetime.date.today().year - self.birthdate.year

    @age.setter
    ##装饰器
    def age(self,value):
        raise AttributeError('禁止赋值年龄！')

    @age.deleter
    def age(self):
        raise ArithmeticError('年龄不能删除')


    # def get_age(self):
    #     return datetime.date.today().year - self.birthdate.year

if __name__ == '__main__':
    s = Student('Tom',datetime.date(1992,3,1))
    print(s.birthdate)
    print(s.age)

    s.birthdate = datetime.date(1996,8,26)
    print(s.birthdate)
    print(s.age)

输出
1992-03-01
27
1996-08-26
23

• 更改年龄报错

import datetime

class Student:

    def __init__(self,name,birthdate):
        self.name = name
        self.birthdate = birthdate

    @property
    ##属性,好处进一步过滤
    def age(self):
        return datetime.date.today().year - self.birthdate.year

    @age.setter
    ##装饰器
    def age(self,value):
        raise AttributeError('禁止赋值年龄！')

    @age.deleter
    def age(self):
        raise ArithmeticError('年龄不能删除')


if __name__ == '__main__':
    s = Student('Tom',datetime.date(1992,3,1))
    print(s.birthdate)
    print(s.age)

    s.birthdate = datetime.date(1996,8,26)
    s.age = 20
    print(s.birthdate)
    print(s.age)

输出
Traceback (most recent call last):
1992-03-01
File “F:/teacher/pythonbasetry/day7/Test.py”, line 33, in
s.age = 20
27
File “F:/teacher/pythonbasetry/day7/Test.py”, line 17, in age
raise AttributeError(‘禁止赋值年龄！’)
AttributeError: 禁止赋值年龄！

继承示例

1. Employee和Programer类 单继承

import datetime

class Employee:
    def __init__(self,name,birthdate,department,salary):
        self.name = name
        self.birthdate = birthdate
        self.department = department
        self.salary = salary

    def give_raise(self,percent,bonus=.0):
        self.salary = self.salary * (1 + percent + bonus)

    @property
    def age(self):
        return datetime.date.today().year - self.birthdate.year

    def __repr__(self):
        return '<员工 ：{}>'.format(self.name)

    def working(self):
        print ('员工 : {} 工作ing'.format(self.name))


class Programer(Employee):
    def __init__(self,name,birthdate,department,salary,specialty,project):
        ##基类
        super().__init__(name,birthdate,department,salary)
        self.specialty = specialty
        self.project = project

    def working(self):
        print('程序猿：{} 在开发:{}'.format(self.name,self.project))

if __name__ == '__main__':
    p = Programer('kitty',datetime.date(1996,8,26),'tech',8000,'python','cv')
    print(p)
    print(p.department)
    print(p.birthdate)
    print(p.salary)
    p.give_raise(.2,.1)
    print(p.salary)
    p.working()
    print(p.age)

输出
<员工 ：kitty>
tech
1996-08-26
8000
10400.0
程序猿：kitty 在开发:cv
23
注：注意super中参数顺序
报错
return datetime.date.today().year - self.birthdate.year AttributeError: ‘str’ object has no attribute ‘year’
是因为参数顺序错误

2. Employee、Programer、HR类 多继承易混乱

import datetime

class Employee:
    def __init__(self,name,birthdate,department,salary):
        self.name = name
        self.birthdate = birthdate
        self.department = department
        self.salary = salary

    def give_raise(self,percent,bonus=.0):
        self.salary = self.salary * (1 + percent + bonus)

    @property
    def age(self):
        return datetime.date.today().year - self.birthdate.year

    def __repr__(self):
        return '<员工 ：{}>'.format(self.name)

    def working(self):
        print ('员工 : {} 工作ing'.format(self.name))

class Programer(Employee):
    def __init__(self,name,birthdate,department,salary,specialty,project):
        ##基类
        super().__init__(name,birthdate,department,salary)
        self.specialty = specialty
        self.project = project

    def working(self):
        print('程序猿：{} 在开发:{}'.format(self.name,self.project))

class HR(Employee):
    def __init__(self,name,birthdate,department,salary,level = 1):

        ##多继承不建议supersuper().__init__()
        Employee.__init__(self,name,birthdate,department,salary)
        self.level = level
    def working(self):
        print('人事:{}面试ing'.format(self.name))

if __name__ == '__main__':
    p = Programer('kitty',datetime.date(1996,8,26),'tech',8000,'python','cv')
    print(p)
    print(p.department)
    print(p.birthdate)
    print(p.salary)
    p.give_raise(.2,.1)
    print(p.salary)
    p.working()
    print(p.age)

    hr = HR('haha',datetime.date(1992,8,22),'人事',9000,2)
    hr.working()

多态示例

同一类型的不同实例对同一消息做出不同响应

• 包含关联

import datetime

class Department:
    def __init__(self,department,phone,manager):
        self.department = department
        self.phone = phone
        self.manager = manager

    def __repr__(self):
        return '部门:{}'.format(self.department)


class Employee:
    def __init__(self,name,birthdate,department:Department,salary):
        self.name = name
        self.birthdate = birthdate
        self.department = department
        self.salary = salary

    def give_raise(self,percent,bonus=.0):
        self.salary = self.salary * (1 + percent + bonus)

    @property
    def age(self):
        return datetime.date.today().year - self.birthdate.year

    def __repr__(self):
        return '<员工 ：{}>'.format(self.name)

    def working(self):
        print ('员工 : {} 工作ing'.format(self.name))

class Programer(Employee):
    def __init__(self,name,birthdate,department,salary,specialty,project):
        ##基类
        super().__init__(name,birthdate,department,salary)
        self.specialty = specialty
        self.project = project

    def working(self):
        print('程序猿：{} 在开发:{}'.format(self.name,self.project))

class HR(Employee):
    def __init__(self,name,birthdate,department,salary,level = 1):
		##多继承不建议supersuper().__init__()
        Employee.__init__(self,name,birthdate,department,salary)
        self.level = level
    
    def working(self):
        print('人事:{}面试ing'.format(self.name))

if __name__ == '__main__':
    dep = Department('tech','010','Lily')
    #department use dep
    p = Programer('kitty',datetime.date(1996,8,26),dep,8000,'python','cv')
    p.give_raise(.2,.1)
    print(p.salary)
    print(p.department)
    print(p.department.phone)