Magic Methods 5

>>> class MyProperty:
	def __init__(self, fget=None, fset=None, fdel=None):
		self.fget = fget
		self.fset = fset
		self.fdel = fdel
	def __get__(self, instance, owner):
		return self.fget(instance)
	def __set__(self, instance, value):
		self.fset(instance, value)
	def __delete__(self, instance):
		self.fdel(instance)

		
>>> class C:
	def __init__(self):
		self._x = None
	def getX(self):
		return self._x
	def setX(self, value):
		self._x = value
	def delX(self):
		del self._x
	x = MyProperty(getX, setX, delX)

	
>>> c = C()
>>> c.x = 'X'
>>> c.x
'X'
>>> del c.x

class Celsius:
    def __init__(self, value = 26.0):
        self.value = float(value)
    def __get__(self, instance, owner):
        return self.value
    def __set__(self, instance, value):
        self.value = float(value)
        
class Fahrenheit:
    def __get__(self, instance, owner):
        return instance.cel * 1.8 + 32.0
    def __set__(self, instance, value):
        instance.cel = (float(value) - 32.0) / 1.8

class Temperature:
    # 定义cel属性的Celsius类
    cel = Celsius()
    # 定义fah属性的Fahrenheit类
    fah = Fahrenheit()

>>> temp = Temperature()
>>> temp
<__main__.Temperature object at 0x105815438>
>>> temp.cel
26.0
>>> temp.cel = 40
>>> temp.cel
40.0
>>> temp.fah
104.0
>>> temp.fah = 100
>>> temp.cel
37.77777777777778