python中的@property的用法详解

>>> class Goods():
        def __init__(self,unit_price,weight):
            self.unit_price = unit_price
            self.weight = weight
        @property
        def price(self):
            return self.unit_price * self.weight
>>> lemons = Goods(7,4)
>>>
>>> lemons.price
28

>>> class Lemons():
        def __init__(self,unit_price=7):
            self.unit_price = unit_price
        def get_unit_price(self):
            return self.unit_price
        def set_unit_price(self,new_unit_price):
            self.unit_price = new_unit_price
        def del_unit_price(self):
            del self.unit_price
        x = property(get_unit_price, set_unit_price, del_unit_price)
>>> fruit = Lemons()
>>> 
>>> fruit.x                         #调用 fruit.x 触发 get_unit_price
7
>>> 
>>> fruit.x = 9                     #调用 fruit.x = 9 触发 set_unit_price
>>> 
>>> fruit.x
9
>>> 
>>> fruit.unit_price                #调用 fruit.unit_price 触发 get_unit_price
9
>>> del fruit.x                     #调用 del fruit.x 触发 del_unit_price 
>>> 
>>> fruit.unit_price
Traceback (most recent call last):
  File "<pyshell#23>", line 1, in <module>
    l.unit_price
AttributeError: 'Lemons' object has no attribute 'unit_price'

>>>class Watermelon():
       def __init__(self,price):
           self._price = price                  #私有属性，外部无法修改和访问
 
       def get_price(self):
           return self._price
 
       def set_price(self,new_price):
           if new_price > 0:
               self._price = new_price
           else:
               raise 'error:价格必须大于零'

>>>class Watermelon():
       def __init__(self,price):
           self._price = price
       @property                          #使用@property装饰price方法
       def price(self):
           return self._price
       @price.setter                      #使用@property装饰方法，当对price赋值时，调用装饰方法
       def price(self,new_price):
           if new_price > 0:
               self._price = new_price
           else:
               raise 'error:价格必须大于零'
>>> watermelon = Watermelon(4)
>>> 
>>> watermelon.price
4
>>> 
>>> watermelon.price = 7
>>> 
>>> watermelon.price
7