inheritance in python : not getting expected o/p

Question

class Employee:

    raise_amount = 1.02

    def __init__(self, first, last, pay):
        self.first = first
        self.last = last
        self.pay = pay
        self.email = first+'.'+last+'@company.com'

    def fullname(self):
        return f"Full name is {self.first} {self.last}"

    def apply_raise(self):
        self.pay = int(self.pay * Employee.raise_amount)


class Developer(Employee):
    raise_amount = 1.10

dev1 = Developer('Test1','User1',20000)
dev2 = Developer('Test2','User2',25000)   

print(dev1.pay)
dev1.apply_raise()
print(dev1.pay)

O/p : 20000 20400

where as the o/p should have been 20000 22000

22000, Because we are overriding the class variable in the subclass

what is that which im doing wrong here

Change Employee.raise_amount to self.raise_amount and think about it — Mad Physicist
– Mad Physicist, Commented Apr 26, 2020 at 5:38

Mad Physicist · Accepted Answer · 2020-04-26 15:26:17Z

2

You should change

self.pay = int(self.pay * Employee.raise_amount)

to

self.pay = int(self.pay * self.raise_amount)

that way, the lookup of the class variable is done the way you expect it.

It will all be less confusing if you use a instance variable instead of a class variable to achieve what you want.

edited Apr 26, 2020 at 15:26

Mad Physicist

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answered Apr 26, 2020 at 5:38

Mike Scotty

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2 Comments

Mad Physicist Over a year ago

It's still a class variable

Mike Scotty Over a year ago

@MadPhysicist yes. That's why I wrote "that way the lookup of the class variable is done the way you expect it." I only mentiond in a side note, that using an instance variable from the start might lead to a less surprising behaviour.

tdelaney · Accepted Answer · 2020-04-26 05:38:14Z

1

You create a subclass but the parent uses Employee.raise_amount for calculations, hard coding the class. Change that to self.raise_amount so that the parent method will use the subclass variable instead.

    def apply_raise(self):
        self.pay = int(self.pay * self.raise_amount)

answered Apr 26, 2020 at 5:38

tdelaney

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Comments

lone_ranger · Accepted Answer · 2020-04-26 05:42:46Z

0

def apply_raise(self): self.pay = int(self.pay * Employee.raise_amount)

try replacing Employee with self

def apply_raise(self): self.pay = int(self.pay * self.raise_amount)

answered Apr 26, 2020 at 5:42

lone_ranger

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