使用類作爲方法裝飾器

Question

雖然有plenty of resources about using classes as decorators，但我一直未能找到任何處理方法的問題。這個問題的目標是解決這個問題。我會發布我自己的解決方案，但當然也邀請其他人發佈他們的解決方案。

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爲什麼「標準」的實施不起作用

與標準的裝飾類實現的問題是，蟒蛇不會造成裝飾功能的綁定方法：

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' 

方法裝飾者需要克服這個障礙。

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要求

從前面的例子中以類，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 

理想的情況下，該功能的__doc__和簽名以及類似的屬性將被保留爲好。

Answer 1

基本「什麼都不做」裝飾類：

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 

，而另一種參數：

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 

這樣的實現讓我們使用的方法裝飾以及功能，所以我認爲這應該被認爲是很好的做法。