How does python deal with this inheritance issue?

Question

class A:
    def __init__(self):
        print('I am A')


class B(A):
    def b(self):
        print('I am B.b')


class C(A):
    def c(self):
        x.b()


if __name__ == '__main__':
    x = B()
    y = C()
    y.c()

How does it work when it comes to 'y.c() '? In C.c(), how can the instance x be called without instantiation before? Thanks a lot, if someone can help.

did you mean self.b()? (x is a global variable instantiated in your "__main__" clause). — thebjorn
– thebjorn, Commented Feb 14, 2019 at 15:06
x is a global variable. You created it outside of any function. — khelwood
– khelwood, Commented Feb 14, 2019 at 15:09

blue note · Accepted Answer · 2019-02-14 15:10:28Z

2

It cannot. In your case, it just happens that when you call x.b() there is a global variable that happens to be named x have type B. It has been initialized at the previous line, with x = B().

This code depends on external variables, and will fail in general. If you want to call the objects own method, use self.b() instead.

answered Feb 14, 2019 at 15:10

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