FAQ: Object-Oriented Programming - Introduction to Object-Oriented Programming

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This community-built FAQ covers the “Introduction to Object-Oriented Programming” exercise from the lesson “Object-Oriented Programming”.

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This exercise can be found in the following Codecademy content:

Learn Intermediate Python 3

FAQs on the exercise Introduction to Object-Oriented Programming

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2

Why can’t we use self.id = self.new_id instead of self.id = Employee.new_id. Don’t they point to the same value?

3 Likes
3

I think self.id is newly introduced to identify an employee id and however the Employee class is already defined will determine the new_id.

4

hello micro4950816268, i have got same question. why can’t we use the self.id = self.new_id instead of self.id = Employee.new_id. Since it is a class variable and we can call it either with the class name or using the self after the init method.

Explain please

5

Why is there ‘None’ in my outputs?

My id is 1
None
My id is 2
None

My code is

# Write your code below
class Employee:
  new_id = 1

  def __init__(self):
    self.id = Employee.new_id
    Employee.new_id += 1

  def say_id(self):
    print('My id is {}'.format(self.id))


e1 = Employee()
e2 = Employee()

print(e1.say_id())
print(e2.say_id())

Thank you.

1 Like
6

Hi,

I believe the None is due to the fact that the say_id method has no return sentence, i.e. it returns nothing or “None”
Try replacing print by return in the method and you’ll see how the None disappears! :slight_smile:

return "My id is {}".format(self.id)

Best

1 Like
8

Alternatively you can just use
e1.say_id()
e2.say_id()

Using print it tries to find a return item and since the function has no such element it prints None

1 Like