FAQ: Object-Oriented Programming - OOP Pillar: Encapsulation

This community-built FAQ covers the “OOP Pillar: Encapsulation” 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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Sorry, I don’t know the rules quite enough, please check if I can say about it here!!! BUt for Russian speaking AND those who are not completely sure that they understand why is it needed to use the concepts “private, protected, public” IF "Python doesn’t have any inbuilt mechanism to prevent access from any member (i.e. all members are public in Python). "
Приватные методы без нижнего подчеркивания и интерфейсы в Python / Хабр
Thank you, dmytrostriletskyi Helped a lot.

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In the course, it says private class member can still be accessed publicly, but when I tried to print the private member in this code, I received an AttributeError. Why is this?

class Employee(): def __init__(self): self.id = None # Write your code below self._id = 0 self.__id = 1 e = Employee() print(dir(e)) print(e.__id)
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Because methods starting with a double underscore __name are treated differently and undergo name mangling: https://docs.python.org/3/reference/expressions.html#atom-identifiers. You’d have to use the mangled name if you really wanted to access the attribute which in this case would be e._Employee__id. Name mangling is pretty uncommon in Python so consider carefully whether or not you actually want to be using it.

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I have a basic question about the terminology used by Codecademy below:

‘An instance variable e is defined …’

Is e in this example not better referred to as a ‘class object’ rather than an ‘instance variable’?
My understanding was that an instance variable can also be called an instance attribute, and refers to attributes which are not shared by the objects that are part of a class. Please let me know if I am mistaken here - appreciate any links to a helpful summary of terminology if relevant!


E is an instance of the class here. An instance attribute is an attribute of the specific instance of the class, e.g. whatever the employee’s id number is would be an attribute of the instance (the specific employee). You’re correct that instance attributes are not necessarily shared by the class, although this may not be the case when working with default parameters in class constructors. Hope this helps!