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Where can we declare the instance variables?

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  1. Inside the constructor using self.
  2. Inside an instance method using self.
  3. Outside the class using the object reference variable.

Inside the constructor using self.

class Test:
    def __init__(self):
        self.a = 10
        self.b = 15

obj = Test() # a , b will be added the object.
print(obj.__dict__) # {'a': 10, 'b': 15}

Inside an instance method using self.

  • We can declare instance variables inside an instance method using the self variable.
  • If we declare an instance variable inside an instance method, that variable will be added to the object when the method is called.
  • If the instance method is not called, those variables will not be added to the object.
class Test:
    def __init__(self):
        self.a = 10
        self.b = 15

    def m1(self):
        self.c = 25

obj = Test() # a , b will be added the object.
obj.m1() # c will be added to the object
print(obj.__dict__) # {'a': 10, 'b': 15, 'c': 25}

Outside the class using the object reference variable.

class Test:
    def __init__(self):
        self.a = 10
        self.b = 15

    def m1(self):
        self.c = 25

obj = Test() # a , b will be added the object.
obj.m1() # c will be added to the object
obj.d = 35 # d will be added to the object
print(obj.__dict__) # {'a': 10, 'b': 15, 'c': 25, 'd': 35}

 

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