从父类执行时父类实例变量被覆盖

Question

class Foo:

    def __init__(self):
        self.model = 'A'


    def create(self):
        print(f'Model in class {self.model}')



class Bar(Foo):
    def __init__(self):
        self.model = 'B'


    def save(self):
        super().create()

        print(f'Model in class Bar {self.model}')


bar = Bar()
bar.save()

Output:

Model in class Foo B

Model in class Bar B

Why is the variable model in class Foo getting overridden when it is in the parent class. Is this what should really happen? I want to make it the print A when it is executing from the parent class. What's going wrong here in the code

Answer 1

Nothing is wrong. Everything works as expected. This line executes initializer of Class Bar and from this moment bar.model is pointing to string B

bar=Bar()

When you call the parent class method it is indeed executed (what you can observe by the output of print), but this doesn't change the value of attribute model of object bar .

Answer 2

Why is the variable model in class Foo getting overridden when it is in the parent class. Is this what should really happen?

The variable model defined in the class Foo is not getting overridden, in fact it's never being set in the base class.

I want to make it the print A when it is executing from the parent class

Then you need to change your constructor:

class Bar(Foo):
    def __init__(self):
        super().__init__()


    def save(self):
        print(f'Model in class Bar {self.model}')