CODEWITHSUNDEEP
pythonvariablesinstance
BLACKMAMBA
BLACKMAMBA

Reputation: 725

Python Variable Access

class A:
    def __init__(self):
        self.i = 0
    def demo(self):
        self.a=1

class B(A):
    def __init__(self, j = 0):
        super().__init__()
        self.j = j
        print(self.i)
        self.demo()
    def demo(self):
        print(self.a)

def main():
    b = B()
    print(b.i)
    print(b.j)
main()

why am i not able to access self.a inside class b does prefixing a variable with self. will make it an instance variable Thanks

Upvotes: 0

Views: 75

Answers (4)

Kenly
Kenly

Reputation: 26688

Because you overwrite demo method on B class.
If you want to access self.a add it to __init__ method of A class or call parent demo method like this: 

   def demo(self):
       super().demo()
       print(self.a)

Upvotes: 1

Clodion
Clodion

Reputation: 1017

Because class A.demo() is not executed:
class A: def init(self): self.i = 0 def demo(self): self.a=1

class B(A):
    def __init__(self, j = 0):
        super().__init__()
        self.j = j
        print(self.i)
        super().demo()
        self.demo()
    def demo(self):
        print(self.a)

def main():
    b = B()
    print(b.i)
    print(b.j)

main()

Upvotes: 0

TigerhawkT3
TigerhawkT3

Reputation: 49318

When you include a demo method for both classes, the most recently-defined one masks the others. Since you define B after you define A but before you call any of the methods in A, demo will try to access a variable that was never defined. You should either call demo within A (in __init__, probably), or change the name of demo in B to something unique, which will allow you to access both methods (probably the best approach, since they do different things and you want to make use of both).

Upvotes: 4

Anthony Kong
Anthony Kong

Reputation: 40624

It is because instance variable b is not initiated within __init__ of A

Upvotes: 0

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