如何将值从一个类传递到另一个类，其中第一个类有来自第二个类的对象，但反之亦然？

class ClassA:
    def __init__(self, class_b):
        self.class_b = class_b
        self.value_a = None

    def set_value_from_b(self):
        self.value_a = self.class_b.get_value_a()

    def get_value_a(self):
        return self.value_a

class ClassB:
    def __init__(self, class_a):
        self.class_a = class_a
        self.value_b = None

    def set_value_from_a(self):
        self.value_b = self.class_a.get_value_a()

    def get_value_a(self):
        return self.class_a.value_a if self.class_a else None

# 创建对象并传递引用
class_b_instance = ClassB(None)
class_a_instance = ClassA(class_b_instance)
class_b_instance.class_a = class_a_instance

# 设置值并传递
class_a_instance.value_a = "Hello from ClassA"
class_a_instance.set_value_from_b()
class_b_instance.set_value_from_a()

print(class_a_instance.value_a)  # 输出: Hello from ClassA
print(class_b_instance.value_b)  # 输出: Hello from ClassA

import weakref

class ClassA:
    def __init__(self, class_b):
        self.class_b = weakref.ref(class_b)
        self.value_a = None

class ClassB:
    def __init__(self, class_a):
        self.class_a = weakref.ref(class_a)
        self.value_b = None