Python——类的设计详解

Python——类的设计详解

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Python和OOP

Python的OOP实现与Java类似，可以概括为三个概念：

1.【继承】继承是基于Python中的属性查找(在X.name表达式中)
2.【多态】在X.method方法中，method的意义取决于X的类型
3.【封装】方法和运算符实现行为，数据隐藏默认是一种惯例

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OOP和继承：“是一个”关系

举例说明：披萨店团队可以通过文件employees.py中的四个类来定义。最通用的类Employee提供共同行为，例如，加薪(giveRaise)和打印(__repr__)。员工有两种，所以Employee有两个子类：Chef和Server(厨师和服务员)。这两个子类都会覆盖继承的work方法来打印更具体的信息。最后，披萨机器人是由更具体的类来模拟：PizzaRobot是一种Chef，也是一种Employee。以OOP术语来看，这些关系为“是一个”(is-a)链接：机器人是一个主厨，而主厨是一个员工。代码编写如下：

#File employees.py

class Employee:
    def __init__(self,name,salary = 0):
        self.name = name
        self.salary = salary
    def giveRaise(self,percent):
        self.salary = self.salary + (self.salary * percent)
    def work(self):
        print(self.name,'does stuff')
    def __repr__(self):
        return ''%(self.name,self.salary)

class Chef(Employee):
    def __init__(self,name):
        Employee.__init__(self,name,50000)
    def work(self):
        print(self.name,"makes food")

class Server(Employee):
    def __init__(self,name):
        Employee.__init__(self,name,40000)
    def work(self):
        print(self.name,'interfaces with customer')

class PizzaRobot(Chef):
    def __init__(self,name):
        Chef.__init__(self,name)
    def work(self):
        print(self.name,'makes pizza')


if __name__ == '__main__':
    bob = PizzaRobot('bob')
    print(bob)
    bob.work()
    bob.giveRaise(.2)
    print(bob)
    print()

    for klass in Employee,Chef,Server,PizzaRobot:
        obj = klass(klass.__name__)
        obj.work()

bob makes pizza


Employee does stuff
Chef makes food
Server interfaces with customer
PizzaRobot makes pizza

def __repr__(self):
        return '