CODEWITHSUNDEEP
pythonpython-3.xclassoop
Mike
Mike

Reputation: 89

OOP: Init method questions

I have two questions regarding the code below.

  1. What is the difference between self.a=self.test1() and a=self.test1()? One is class field and other one is object field?
  2. Why cannot I define result = self.a+self.b? How to correct it?
class Test():
    def __init__(self):
        self.a=self.test1()
        a=self.test1()
        self.b=Test.test2()
    
    result = self.a+self.b    
    def test1(self):
        a=100
        return a
    @classmethod
    def test2(cls):
        b=200
        return b

    @staticmethod
    def test3():
        print("Testing3 is calling ")
        c=500
        return c

Upvotes: 0

Views: 95

Answers (2)

Skk
Skk

Reputation: 188

self.a is a property in this class. It will remain accessible throughout functions in the Test() class. a = self.test1(), however, goes away once __init__(self) finishes, because a is local to __init__(self).

For result = self.a + self.b, I assume you want a variable called result calculated after self.a and self.b is defined? At that indentation level a statement like this is usually not allowed (I could be wrong), usually a declaration of a property of a class happens here.

Upvotes: 1

chepner
chepner

Reputation: 531055

self.a = self.test1() creates an instance attribute named a. The attribute will be accessible from the object anywhere you have a reference to the object.

a = self.test1() defines a local variable named a. It will go out of scope once __init__ returns.

result = self.a + self.b doesn't work because it is in a context where self is not defined. self is just the (conventional) name of the first parameter of an instance method. It's not defined in the namespace of the class statement itself.

Upvotes: 2

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