inheritance in Python deletes the original value

Question

I have programmed a small inheritance problem in Python:

class Worker:


    def __init__(self,cod):
        self.cod=cod
        self.wage=0

class FactoryWorker(Worker):
    def __init__(self,cod,wage):
        Worker.__init__(self,cod,wage)
        Worker.wage=wage*1.10

    def printWage(self):
        return Worker.wage

class OfficeWorker(Worker):
    def __init__(self,cod,payperHour,numberHours):
        Worker.__init__(self,cod)
        self.payperHour=payperHour
        self.numberHours=numberHours

    def printWage(self):
        Worker.wage=self.payperHour*self.numberHours
        return Worker.wage

The problem that I have is when I make a couple of objects:

w1=FactoryWorker(2130,4000)
w1.printWage()

prints 4400

w2=OfficeWorker(1244,50,100)
w2.printWage()

prints 5000

but if I do again:

w1.printWage()

it does not print the original 4400, but it prints instead 5000

why is that? I want the variable wage to be declared as an attribute of the class Worjer and not individually in each one of the subclasses.

Any help?

Answer 1

Your problem is that Worker.wage is a class member, meaning that all instances of the class will share the same value. What you want is simply self.wage , which is an instance member, meaning that each instance of the class will have its own value.

Answer 2

You appear to know that you should refer to instance attributes via self , since you are doing that with payperhour etc. So I don't know why you aren't also doing it with wage .

class FactoryWorker(Worker):
    def __init__(self,cod,wage):
        super(FactoryWorker, self).__init__(self,cod,wage)
        self.wage=wage*1.10

(Also note the more Pythonic and flexible use of super , rather than calling the superclass explicitly.)