exhibit a

exhibit_a.py

class A:
    some_value = {}

class B(A):

    def modify_value(self):
        self.some_value.update({"some_value": "b"})

class C(A):

    def modify_value(self):
        self.some_value.update({"some_value": "c"})

if __name__ == '__main__':
    b = B()
    c = C()

    c.modify_value()
    print(b.some_value)
    b.modify_value()
    print(b.some_value)
    c.modify_value()
    print(c.some_value)

# {'some_value': 'c'}
# {'some_value': 'b'}
# {'some_value': 'c'}