How do I change the variable value of one of the two classes?

class test1:
    def __init__(self):
        pass
    def test1_1(self):
        self.a = 0
        print(self.a)

class test2:
    def __init__(self):
        pass
    def test2_2(self):
        self.aaa = test1()
        self.aaa.a = 9999999999
        print(self.aaa)

test1().test1_1()
test2.test2_2()