FAQ: Object-Oriented Programming - Review

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This community-built FAQ covers the “Review” 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

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[jamesw_miller]

Up to this point in the course there has only been one short video on decorators and then the exercise on @abstractmethod. In this review suddenly the @property and @username.setter decorators appear out of no where. It is very frustrating when content comes up in a review that has not been covered in the lessons. After some research (on another site), it appears these special decorators are very useful to mastering OOP, so I wonder why they have not been covered, yet appear in the review? It would be great if this course was amended so that they are included.

edit: I see now that the property decorator is covered in the section following the review and the project. Perhaps consider moving this section to before the review/project. The fact I went to a different site to look it up thinking id missed something is evidence enough the order needs changing!

[heydavidr]

What is the purpose of the following piece of code encapsulated in the AbstractEmployee class?

@abstractmethod
  def say_id(self):
    pass

Why wouldn’t you just add a new say_id method to the other classes / sub classes as neccesary?

from abc import ABC, abstractmethod

class AbstractEmployee(ABC):
  new_id = 1
  def __init__(self):
    self.id = AbstractEmployee.new_id
    AbstractEmployee.new_id += 1

  @abstractmethod
  def say_id(self):
    pass

class User:
  def __init__(self):
    self._username = None

  @property
  def username(self):
    return self._username

  @username.setter
  def username(self, new_name):
    self._username = new_name

class Meeting:
  def __init__(self):
    self.attendees = []
  
  def __add__(self, employee):
    print("{} added.".format(employee.username))
    self.attendees.append(employee.username)

  def __len__(self):
    return len(self.attendees)

class Employee(AbstractEmployee, User):
    def __init__(self, username):
      super().__init__()
      User.__init__(self)
      self.username = username

    def say_id(self):
      print("My id is {}".format(self.id))
 
    def say_username(self):
      print("My username is {}".format(self.username))

[phamsonn]

I believe it is the purpose of the abstraction, which enforces that the sub-classes must have their own self-defined say_id methods.

[eximio]

I am finding grasping OOP to be quite difficult. It’s abstract (not referring to the pillar) to a degree that I have not practiced for a long time. I think simply repeating several exercises from simple to moderate (save the complex for later) is the only way I will absorb it. Where can I go for such exercises?

[nouma.mdw]

Finding the same struggte as @jamesw_miller.
If the decorators @property and the decorator for setter appear later in the lesson. How about just leaving them out of the review to prevent confusion?