Python中的Decorators表面看起来很像C#的Attribute，其实不然，Python的Decorators和C#的Attribute完全是两个东西。Python的Decorators让我想到了设计模式中的装饰者模式（Decorator Pattern）。
Decorator Pattern
Attach additional responsibilities to an object dynamically.
Decorators provide a flexible alternative to subclassing for extending functionnality.
Decorators provide a flexible alternative to subclassing for extending functionnality.
Python中的通过Decorators对函数、方法或类进行装饰，从而达到增加对象的职责，或控制对象调用的作用。而C#的Attribute仅仅是起到元数据标识作用，最终通过反射获取这些特定信息。
先来个简单的示例，先定义一个Coffee类，
class Coffee(object):
def get_cost(self):
return 1.0
coffee = Coffee()
print coffee.get_cost() # 1.0
def get_cost(self):
return 1.0
coffee = Coffee()
print coffee.get_cost() # 1.0
这时，我想通过装饰者模式计算Milk的价格，通常这样实现：
class Milk(Coffee):
def __init__(self, coffee):
self.coffee = coffee
def get_cost(self):
return self.coffee.get_cost() + 0.5
coffee = Coffee()
coffee = Milk(coffee)
print coffee.get_cost() # 1.5
def __init__(self, coffee):
self.coffee = coffee
def get_cost(self):
return self.coffee.get_cost() + 0.5
coffee = Coffee()
coffee = Milk(coffee)
print coffee.get_cost() # 1.5