class GlobalInterface:
    _instance = None

    def __new__(cls, *args, **kwargs):
        if not cls._instance:
            cls._instance = super(GlobalInterface, cls).__new__(cls, *args, **kwargs)
        return cls._instance

    def __init__(self):
        self.shared_data = {}

    def set_data(self, key, value):
        self.shared_data[key] = value

    def get_data(self, key):
        return self.shared_data.get(key, None)


if __name__ == '__main__':
    interface = GlobalInterface()
    interface2 = GlobalInterface()

    interface.set_data('key1', 'value1')

    print(interface2.get_data('key1'))