__bases__ misleading error message

[Terry Reedy]

On 1/24/2015 4:14 PM, Mario Figueiredo wrote:
> In article <54c39366$0$13006$c3e8da3$5496439d at news.astraweb.com>,
> steve+comp.lang.python at pearwood.info says...
>>>          AttributeError: 'Sub' instance has no attribute '__bases__',
>>>          AttributeError: 'foo' object has no attribute '__bases__'
>>
>> The first would be nice. The second is impossible: objects may have no name,
>> one name, or many names, and they do not know what names they are bound to.
>> So the Sub instance bound to the name 'foo' doesn't know that its name
>> is 'foo', so it cannot display it in the error message.
>
> Thanks for the information! :)
>
> But that begs the OT question: How does Python maps names to memory
> addresses in the interpreter?

Python the language maps names to objects that have identity, type, and 
value.  The CPython implementation does the mapping with a hash table 
and C pointers (to computer memory addresses), but addresses are not 
part of the language definition.  Neuroscientists still puzzle over how 
we do such mapping.

>      "__main__"
>      from module import a_name

A module is a namespace associating names with objects.  This statememt 
says to import the a_name to object association from module and add it 
to __main__

>      y = a_name + 1

This statement uses the imported association in __main__ to access the 
object and add 1, and bind 'y' to the resulting object.

-- 
Terry Jan Reedy