[Python-Dev] variable name resolution in exec is incorrect

[Guido van Rossum]

On Wed, May 26, 2010 at 5:53 PM, Colin H <hawkett at gmail.com> wrote:
>   Thanks for the possible workaround - unfortunately 'stuff' will
> contain a whole stack of things that are not in 'context', and were
> not defined in 'user_code' - things that python embeds - a (very
> small) selection -
>
> {..., 'NameError': <type 'exceptions.NameError'>, 'BytesWarning':
> <type 'exceptions.BytesWarning'>, 'dict': <type 'dict'>, 'input':
> <function input at 0x10047a9b0>, 'oct': <built-in function oct>,
> 'bin': <built-in function bin>, ...}
>
> It makes sense why this happens of course, but upon return, the
> globals dict is very large, and finding the stuff you defined in your
> user_code amongst it is a very difficult task.  Avoiding this problem
> is the 'locals' use-case for me.  Cheers,

No, if taken literally that doesn't make sense. Those are builtins. I
think you are mistaken that each of those (e.g. NameError) is in stuff
-- they are in stuff['__builtins__'] which represents the built-in
namespace. You should remove that key from stuff as well.

--Guido

> Colin
>
> On Thu, May 27, 2010 at 1:38 AM, Guido van Rossum <guido at python.org> wrote:
>> This is not easy to fix. The best short-term work-around is probably a
>> hack like this:
>>
>> def define_stuff(user_code):
>>  context = {...}
>>  stuff = {}
>>  stuff.update(context)
>>  exec(user_code, stuff)
>>  for key in context:
>>    if key in stuff and stuff[key] == context[key]:
>>      del stuff[key]
>>  return stuff
>>
>> --
>> --Guido van Rossum (python.org/~guido)
>>
>



-- 
--Guido van Rossum (python.org/~guido)