Object Oriented Programming Python - Class properties

Question

I am trying to understand class properties in Python OO (Object Oriented).

Let's say I have the following code.

    class Testing():
        surname = "Doe"

        def __init__(self):
            print(surname)

If we print surname, as shown above, it will throw the following error: NameError: name 'surname' is not defined. So, how is this class property accessible from outside or inside the class?

Local variables work inside class definitions the same way they work everywhere else: they are available locally and not outside whatever scope they are in (but can be accessed from inner scopes). — juanpa.arrivillaga, Jun 14 '17 at 17:47
The question still says "I am trying to understand about local variables in Python, specifically in OOP". — Barmar, Jun 14 '17 at 17:48
@Barmar well, now it says "Object Oriented Programming Python - Class properties" but again, this has nothing to do with OOP, or class properties for that matter. — juanpa.arrivillaga, Jun 14 '17 at 17:49
`surname` is not a class property, class attributes must be part of `self.surname`, `surname` is different to `self.surname` — eyllanesc, Jun 14 '17 at 17:49
@juanpa.arrivillaga He changed the title, he didn't change the text of the question. — Barmar, Jun 14 '17 at 17:50
@eyllanesc to be pedantic, `self.surname` would be an *instance attribute*. Class-level attributes belong to the class, instance attributes belong to the instance. — juanpa.arrivillaga, Jun 14 '17 at 17:51
I think you should read [this](https://stackoverflow.com/questions/291978/short-description-of-the-scoping-rules) q/a. — juanpa.arrivillaga, Jun 14 '17 at 17:51

score 2 · Answer 1 · answered Jun 14 '17 at 17:54

surname is only available inside the __init__ method. If you want to access it anywhere else you should do self.surname = 'Doe' or Testing.surname = 'Doe'. Note that self is a reference to the instance.

Usually class attributes are declared inside the class like this:

class Testing:
     surname = 'Doe'

You could access them and/or reassign them by using Testing.surname.

score 0 · Answer 2 · answered May 11 '23 at 08:27

0

Your code must read as

    class Testing():
        surname = "Doe"

        def __init__(self):
            print(self.surname)  # <<< note `self.` prefix

answered May 11 '23 at 08:27

jno

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Object Oriented Programming Python - Class properties

2 Answers2