使用类作为方法装饰器

Question

虽然有plenty of resources about using classes as decorators，但我一直未能找到任何处理方法的问题。这个问题的目标是解决这个问题。我会发布我自己的解决方案，但当然也邀请其他人发布他们的解决方案。

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为什么“标准”的实施不起作用

与标准的装饰类实现的问题是，蟒蛇不会造成装饰功能的绑定方法：

class Deco: 
    def __init__(self, func): 
     self.func= func 

    def __call__(self, *args): 
     self.func(*args) 

class Class: 
    @Deco 
    def hello(self): 
     print('hello world') 

Class().hello() # throws TypeError: hello() missing 1 required positional argument: 'self' 

方法装饰者需要克服这个障碍。

---

要求

从前面的例子中以类，下面的事情也有望可以使用：

>>> i= Class() 
>>> i.hello() 
hello world 
>>> i.hello 
<__main__.Deco object at 0x7f4ae8b518d0> 
>>> Class.hello is Class().hello 
False 
>>> Class().hello is Class().hello 
False 
>>> i.hello is i.hello 
True 

理想的情况下，该功能的__doc__和签名以及类似的属性将被保留为好。

Answer 1

基本“什么都不做”装饰类：

import inspect 
import functools 
from copy import copy 


class Deco: 
    def __init__(self, func): 
     self.__self__ = None # "__self__" is also used by bound methods 

     functools.update_wrapper(self, func) 

    def __call__(self, *args, **kwargs): 
     # if bound to an object, pass it as the first argument 
     if self.__self__ is not None: 
      args = (self.__self__,) + args 

     #== change the following line to make the decorator do something == 
     return self.__wrapped__(*args, **kwargs) 

    def __get__(self, instance, owner): 
     if instance is None: 
      return self 

     # create a bound copy 
     bound = copy(self) 
     bound.__self__ = instance 

     # update __doc__ and similar attributes 
     functools.update_wrapper(bound, self.__wrapped__) 

     # add the bound instance to the object's dict so that 
     # __get__ won't be called a 2nd time 
     setattr(instance, self.__wrapped__.__name__, bound) 

     return bound 

，而另一种参数：

class DecoWithArgs: 
    #== change the constructor's parameters to fit your needs == 
    def __init__(self, *args): 
     self.args = args 

     self.__wrapped__ = None 
     self.__self__ = None 

    def __call__(self, *args, **kwargs): 
     if self.__wrapped__ is None: 
      return self.__wrap(*args, **kwargs) 
     else: 
      return self.__call_wrapped_function(*args, **kwargs) 

    def __wrap(self, func): 
     # update __doc__ and similar attributes 
     functools.update_wrapper(self, func) 

     return self 

    def __call_wrapped_function(self, *args, **kwargs): 
     # if bound to an object, pass it as the first argument 
     if self.__self__ is not None: 
      args = (self.__self__,) + args 

     #== change the following line to make the decorator do something == 
     return self.__wrapped__(*args, **kwargs) 

    def __get__(self, instance, owner): 
     if instance is None: 
      return self 

     # create a bound copy of this object 
     bound = copy(self) 
     bound.__self__ = instance 
     bound.__wrap(self.__wrapped__) 

     # add the bound decorator to the object's dict so that 
     # __get__ won't be called a 2nd time 
     setattr(instance, self.__wrapped__.__name__, bound) 
     return bound 

这样的实现让我们使用的方法装饰以及功能，所以我认为这应该被认为是很好的做法。