有必要检查flyweight模式中的init状态吗？

Question

下面是一些python书籍中的一个示例：

import weakref
class CarModel:
    _models = weakref.WeakValueDictionary()

    def __new__(cls, model_name, *args, **kwargs):
        """
        :type model_name: str
        """
        model = cls._models.get(model_name)
        if not model:
            model = super().__new__(cls)
            cls._models[model_name] = model
        return model

    def __init__(self, model_name, air=False, tilt=False, cruise_control=False, power_locks=False, alloy_wheels=False, usb_charger=False):
        if not hasattr(self, "initted"):
            self.model_name = model_name
            self.air = air
            self.tilt = tilt
            self.cruise_control = cruise_control
            self.power_locks = power_locks
            self.alloy_wheels = alloy_wheels
            self.usb_charger = usb_charger
            self.initted = True

    def check_serial(self, serial_number):
        print("{0} not yet available on {1}".format(serial_number, self.model_name))

是否真的有必要检查对象是否已初始化？据我所知，__init__函数无论如何只会被调用一次。你知道吗

Answer 1

这是一个有点奇怪的情况，因为它覆盖了新的，所以它可以在存储库中跟踪不同车型的汽车。你知道吗

所以你可以：

c = CarModel('ford')
<cars.CarModel at 0x7fb39dfc1be0>

c = CarModel('vw')
<cars.CarModel at 0x7fb39df72668>

c = CarModel('ford')
<cars.CarModel at 0x7fb39dfc1be0>

注意对CarModel('ford')的第二个调用实际上如何返回相同的对象（0x7fb39dfc1be0）？__新的uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu。你知道吗

需要注意的一点是，第二次传递的额外参数被完全忽略（因为它没有通过not hasattr(self, "initted")测试）。你知道吗