Why do descriptors (and thus properties) only work on attributes.

[Steven Bethard]

Steve Holden wrote:
> Steven Bethard wrote:
> 
>> Antoon Pardon wrote:
>>
>>> Can anyone explain why descriptors only work when they are an attribute
>>> to an object or class.  I think a lot of interesting things one can
>>> do with descriptors would be just as interesting if the object stood
>>> on itself instead of being an attribute to an other object.
>>
>> Not sure what "stood on itself" really means, but if you just want to 
>> be able to have module-level properties, you can do something like:
>>
> Think in non-English (stand outside yourself?) for a second, rememberinf 
> Antoon is Belgian (if you knew that):
> 
>    "on" => "by"
> 
>    "stood on itself" => "stood by itself"
>                      => "standalone"
> 

Sorry, I gathered that this meant "standalone".  My problem was that I'm 
not sure what "standalone" means in the context of descriptors. 
Descriptors are invoked when dotted-attribute access is used.  When 
exactly is he proposing "standalone" descriptors would be invoked?

STeVe