Decorating methods - where do my arguments go?

Mikael Olofsson mikael at isy.liu.se
Tue May 12 12:04:39 CEST 2009


Michele Simionato wrote:
 > Still it turns something which is a function into an object and
 > you lose the docstring and the signature. pydoc will not be too
 > happy with this approach.

Duncan Booth wrote:
> I don't know why Mikael wants to use a class rather than a function
> but if he wants to save state between calls this isn't going to help.

I've never used decorators before, and that's the main reason for my 
confusion. I have found myself in a situation where I think that 
decorators is the way to go. So I tried to find information about how to 
write them the usual way: Googling and browsing documentation. I found 
examples using both functions and classes, but not much explanation of 
what's going on, especially not in the class case. I didn't find any 
arguments for favouring any of those alternatives. Actually, most 
examples I found did not even include the definition of the actual 
decorator or any information about where they might come from, only the 
@-row.

Based on the above observations, I assumed that both alternatives were 
equally possible. The first answers I got here also led me to believe 
that that was the case. My understanding is that in most cases, you can 
use a callable object instead of a function with little or no practical 
difference, except the syntax of its definition. In my eyes, a class 
definition looks nicer and is more readable than a nested function. 
Therefore, I tend to define a class with a __call__ method and helper 
methods instead of nested functions, if I find the need.

Practicality beats purity, and it seem like using a class for decoration 
is a lot more hassle than using a function. I fold.

/MiO



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