具有相似吸气剂/二传手函数的多个属性

Question

定义具有大量属性的类的最干净方法是什么，每个属性都使用不同的参数调用相同的 setter 函数？

以下是我想要实现的目标。 这三个属性(red_LED等(中的每一个在设置时调用相同的 TalkToHardware(( 函数，但地址不同。 如您所见，这有效，但类定义冗长且笨拙。 它也容易出错。

class Hardware_Controller(object):
    def __init__(self):
        self.red_LED_address = 0
        self.blue_LED_address = 1
        self.green_LED_address = 2
    @property
    def red_LED(self):
        return self._red_LED_status
    @red_LED.setter
    def red_LED(self,value):
        self.TalkToHardware(self.red_LED_address,value)
        self._red_LED_status = value
    @property
    def blue_LED(self):
        return self._red_LED_status
    @blue_LED.setter
    def blue_LED(self,value):
        self.TalkToHardware(self.blue_LED_address,value)
        self._blue_LED_status = value
    @property
    def green_LED(self):
        return self._red_LED_status
    @green_LED.setter
    def green_LED(self,value):
        self.TalkToHardware(self.green_LED_address,value)
        self._green_LED_status = value
    def TalkToHardware(self,address,value):
        print('Sending %i to address %i' % (value,address))
if __name__ == "__main__":
    a = Hardware_Controller()
    a.red_LED = 1
    a.green_LED = 0
    print(a.red_LED)

输出：

Sending 1 to address 0
Sending 0 to address 2
1

---

我希望类定义看起来更像这样：

class Hardware_Controller(object):
    def __init__(self):
        self.red_LED_address = 0
        self.blue_LED_address = 1
        self.green_LED_address = 2
        self.red_LED = some_magic(self.red_LED_address)
        self.blue_LED = some_magic(self.blue_LED_address)
        self.green_LED = some_magic(self.green_LED_address)
    def some_magic(address):
        # Do magic things
        pass

有没有一种干净的方法来实现这一点，仍然能够直接访问每个LED，如第一个示例的主要功能所示？

Answer 1

您可以创建一个函数，该函数仅定义并返回所需的property类实例，然后使用它来定义类，从而摆脱所有重复的代码^✶。

(如果不是很明显，下面代码中的LED_property()函数对应于您问题中名为some_magic()的函数。

class Hardware_Controller(object):
    def LED_property(color_name):
        """ Create and return a property for the given color_name. """
        address_name = color_name + '_LED_address'
        storage_name = '_' + color_name + '_LED_status'
        @property
        def prop(self):
            return getattr(self, storage_name)
        @prop.setter
        def prop(self, value):
            address = getattr(self, address_name)
            self.TalkToHardware(address, value)
            setattr(self, storage_name, value)
        return prop
    red_LED = LED_property('red')
    blue_LED = LED_property('blue')
    green_LED = LED_property('green')
    def __init__(self):
        self.red_LED_address = 0
        self.blue_LED_address = 1
        self.green_LED_address = 2
    def TalkToHardware(self, address, value):
        print('Sending %i to address %i' % (value, address))
    del LED_property  # Function isn't needed outside class definition.

if __name__ == "__main__":
    a = Hardware_Controller()
    a.red_LED = 1     # -> Sending 1 to address 0
    a.green_LED = 0   # -> Sending 0 to address 2
    print(a.red_LED)  # -> 1

^✶ 类似于 Python Cookbook(第三版(中 David Beazley 和 Brian Jones (2013( 中的配方"9.21 避免重复属性方法"。 我找到了整本书的PDF(8.8 Mb(，食谱在第382页。

Answer 2

也许你可以这样做：

def setter(self, address, value):
    if address == self.red_LED_address:
        attr = '_red_LED_status'
    if address == self.blue_LED_address:
        attr = '_blue_LED_status'
    if address == self.green_LED_address:
        attr = '_green_LED_status'
    self.TalkToHardware(address, value)
    setattr(self, attr, value) ## does this: self._XXX_LED_address = value

这是所有 LED 设置器功能的包罗万象功能。

我希望这是有帮助的！