class Singleton:
    _instance = None

    def __new__(cls):
        if cls._instance is None:
            cls._instance = super().__new__(cls)
            # 这里可以添加初始化代码
        return cls._instance

# 使用Singleton类
instance1 = Singleton()
instance2 = Singleton()

# instance1 和 instance2 是同一个实例
assert instance1 is instance2