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PODecorator classes in Python
 

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    <p>I want to construct classes for use as decorators with the following principles intact:</p> <ol> <li>It should be possible to stack multiple such class decorators on top off 1 function.</li> <li>The resulting function name pointer should be indistinguishable from the same function without a decorator, save maybe for just which type/class it is.</li> <li>Ordering off the decorators should not be relevant unless actually mandated by the decorators. Ie. independent decorators could be applied in any order.</li> </ol> <p>This is for a Django project, and the specific case I am working on now the method needs 2 decorators, and to appear as a normal python function:</p> <pre><code>@AccessCheck @AutoTemplate def view(request, item_id) {} </code></pre> <p>@AutoTemplate changes the function so that instead of returning a HttpResponse, it just returns a dictionary for use in the context. A RequestContext is used, and the template name is inferred from the method name and module.</p> <p>@AccessCheck adds additional checks on the user based on the item_id.</p> <p>I am guessing it's just to get the constructor right and copy the appropriate attributes, but which attributes are these?</p> <p>The following decorator won't work as I describe:</p> <pre><code>class NullDecl (object): def __init__ (self, func): self.func = func def __call__ (self, * args): return self.func (*args) </code></pre> <p>As demonstrated by the following code:</p> <pre><code>@NullDecl @NullDecl def decorated(): pass def pure(): pass # results in set(['func_closure', 'func_dict', '__get__', 'func_name', # 'func_defaults', '__name__', 'func_code', 'func_doc', 'func_globals']) print set(dir(pure)) - set(dir(decorated)); </code></pre> <p>Additionally, try and add "print func.<strong>name</strong>" in the NullDecl constructor, and it will work for the first decorator, but not the second - as name will be missing.</p> <p>Refined <strong>eduffy</strong>'s answer a bit, and it seems to work pretty well:</p> <pre><code>class NullDecl (object): def __init__ (self, func): self.func = func for n in set(dir(func)) - set(dir(self)): setattr(self, n, getattr(func, n)) def __call__ (self, * args): return self.func (*args) def __repr__(self): return self.func </code></pre>
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    1. CO+1 because I'm not sure why someone voted this question down. It's a good question: most decorator questions on SO don't use classes as decorators. Whatever one may think of uses a class instead of a function, it's a valid question and may be fully appropriate to the use case.
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