What should a decorator do if an attribute already exists?

[Steven D'Aprano]

On Monday 16 May 2016 22:20, jmp wrote:

> On 05/10/2016 05:45 PM, Steven D'Aprano wrote:
>> I have a decorator that adds an attribute to the decorated function:
> [snip]
>> I think 5 is clearly wrong, 4 is too difficult, and 3 seems pointless. So I
>> think either 1 or 2 is the right thing to do.
>>
>> Thoughts?
> 
> It depends if the attribute "instrument" is part of the public interface.

Yes it is.

> If not, just find a different name unlikely to clash with an existing
> one *and* raise an exception if it does ever happen anyway.
> 
> If the attribute is part of the public interface but you re using the
> code only internally then 1/ raise an exception, otherwise I don't know :o)
> 
> It seems to me that over-writing silently (or not) may lead to bugs
> difficult to spot.

At this point, I think I will raise a warning. The user can use the warnings 
module to turn that warning into an error, if they want to, otherwise it's not 
necessarily an error.



-- 
Steve