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Date: Mon, 21 Nov 2011 10:06:00 -0500
From: Dave Angel <d@davea.name>
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To: Andrea Crotti <andrea.crotti.0@gmail.com>
Subject: Re: decorators and closures
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On 11/21/2011 09:44 AM, Andrea Crotti wrote:
> With one colleague I discovered that the decorator code is always 
> executed, every time I call
> a nested function:
>
> def dec(fn):
>     print("In decorator")
>     def _dec():
>         fn()
>
>     return _dec
>
> def nested():
>     @dec
>     def fun():
>         print("here")
>
> nested()
> nested()
>
> Will give:
> In decorator
> In decorator
>
> So we were wondering, would the interpreter be able to optimize this 
> somehow?
> I was betting it's not possible, but I'm I would like to be wrong :)
Your function 'nested' isn't nested, 'fun' is.  What you discovered is 
that a decorator is always executed, every time a nested decorated 
function is defined.

You've also ust proved that it would be an incompatible change.  Doesn't 
that answer the question?  An optimizer that changes the behavior isn't 
usually desirable.


-- 

DaveA