setattr using invalid attribute names - bug or feature?

[Yermat]

Peter Hansen wrote:
> Gerson Kurz wrote:
> 
>> I stumbled across this (while using my homebrewn enum class):
>>
>>     class test:
>>         pass
>>
>>     instance = test()
>>     setattr(instance, "THIS :*2+~# IS OBVIOUSLY INVALID", 123)
>>
>> I would've expected some kind of error message here when calling
>> setattr(); after all, its not a regular attribute?
> 
> 
> Okay.  But so what?
> 
> -Peter

And sometime it is usefull to create some attributes that can unlikely 
be used by the programmer (for example for cache or...).

I've seen code on coockbook that were using that property.

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