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PO__decorated__ for python decorators
 

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    <p>As of 2.4 (2.6 for classes), python allows you to decorate a function with another function:</p> <pre><code>def d(func): return func @d def test(first): pass </code></pre> <p>It's a convenient syntactic sugar. You can do all sorts of neat stuff with decorators without making a mess. However, if you want to find out the original function that got decorated you have to jump through hoops (like <code>Cls.method.__func__.__closure__[0].cell_contents</code> or worse).</p> <p>I found myself wishing for a better way and found that there had been some discussion on python-dev about adding a variable called <code>__decorated__</code> to the [new] function returned by the decorator. However, it appears that didn't go anywhere.</p> <p>Being an adventuresome person, and having had pretty heavy python experience for about 4 years, I thought I would look into implementing <code>__decorated__</code> in the python compiler source, just to see how it goes. </p> <p>To be honest I have never delved into the C underneath the hood, so my first hours have been just trying to make sense of how the underlying C code works. So firstly, <strong>what would be the best resources to get my head around what I would have to change/add for <code>__decorator__</code>?</strong></p> <p>Secondly, if a decorator returns a new function then <code>__decorated__</code> would just return the original, decorated function. However, if the decorator returns the original function, what should happen? Here are three options I could think of (the third is my favorite):</p> <ol> <li>Don't add <code>__decorator__</code>.</li> <li>Add <code>__decorator__</code> but set it to None.</li> <li>Add <code>__decorator__</code> and set it to the original function anyway.</li> </ol> <p>So if it were to happen, <strong>what do you think would be the best option?</strong> </p> <p>UPDATE:</p> <p>Someone else <a href="https://stackoverflow.com/questions/3375573/finding-a-functions-parameters-in-python/3501316#3501316">brought to my attention</a> a scenario that I had missed. What happens when the decorator returns neither the original function nor a function that wraps the original? At that point nothing is holding a reference to the original function and it will get garbage collected. (Thanks <a href="https://stackoverflow.com/users/8014/oddthinking">Oddthinking</a>!)</p> <p>So in that case, I think that I would still go with the third option. The object returned by the decorator would gain a <code>__decorated__</code> name that references the original function. This would mean that it would not be garbage-collected. </p> <p>It seems weird to me that the function from a class definition would utterly disappear because you decorated it. In my mind that is even more reason to have a <code>__decorated__</code> attribute applied for every decorator. However, it's more likely that my intuition is faulty and that the current behavior is what most people would expect. <strong>Any thoughts?</strong></p> <p>p.s. this is an extension of an earlier, more general <a href="https://stackoverflow.com/questions/3375573/finding-a-functions-parameters-in-python">question</a> I had. I also went for more info on the first part with a <a href="https://stackoverflow.com/questions/3505029/extending-the-code-of-python-adding-language-features">separate</a> post. </p>
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    1. COso you are thinking about the next step, i.e., how would the decorated function notice that it is decorated? http://stackoverflow.com/questions/3109289/how-can-python-function-access-its-own-attributes :)
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    2. COHow would this work with `@property`? As in, decorators don't have to return functions at all.
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    3. CO@Aaron, I suppose you would add `__decorated__` to whatever is returned, function or not.
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