Python3.x:不继承地访问其他类中的self.xxx变量

class ClassA:
    def __init__(self):
        self.x = 10

class ClassB:
    def __init__(self):
        self.a = ClassA()

    def access_variable(self):
        print(self.a.x)

b = ClassB()
b.access_variable()  # 输出：10

class ClassA:
    def __init__(self):
        self.x = 10

class ClassB:
    def access_variable(self, obj):
        print(obj.x)

a = ClassA()
b = ClassB()
b.access_variable(a)  # 输出：10

class ClassA:
    x = 10

class ClassB:
    def access_variable(self):
        print(ClassA.x)

b = ClassB()
b.access_variable()  # 输出：10