__dict__ attribute for built-in types

[candide]

Le 28/10/2011 00:19, Steven D'Aprano a écrit :
>
> What, you think it goes against the laws of physics that nobody thought
> to mention it in the docs?<wink>


No but I'm expecting from Python documentation to mention the laws of 
Python ...


>
>> But beside this, how to recognise classes whose object doesn't have a
>> __dict__ attribute ?
>
> The same way as you would test for any other attribute.
>
>>>> hasattr(42, '__dict__')
> False
>
>


OK but I'm talking about classes, not instances  : 42 has no __dict__ 
attribute but, may be, 43 _has_ such attribute, who knows in advance ? ;)

Let'have a try :

 >>> hasattr(43, '__dict__')
False
 >>>


so we have proved by induction that no integer instance has a 
dictionnary attribute ;)