[Python-Dev] issue5578 - explanation

[Guido van Rossum]

Well hold on for a minute, I remember we used to have an exec
statement in a class body in the standard library, to define some file
methods in socket.py IIRC.  It's a totally different case than exec in
a nested function, and I don't believe it should be turned into a
syntax error at all. An exec in a class body is probably meant to
define some methods or other class attributes. I actually think the
2.5 behavior is correct, and I don't know why it changed in 2.6.

--Guido

On Tue, Mar 31, 2009 at 8:15 PM, Maciej Fijalkowski <fijall at gmail.com> wrote:
> So. The issue was closed and I suppose it was closed by not entirely
> understanding
> the problem (or I didn't get it completely).
>
> The question is - what the following code should do?
>
> def f():
>  a = 2
>  class C:
>    exec 'a = 42'
>    abc = a
>  return C
>
> print f().abc
>
> (quick answer - on python2.5 it return 42, on python 2.6 and up it
> returns 2, the patch changes
> it to syntax error).
>
> I would say that returning 2 is the less obvious thing to do. The
> reason why IMO this should
> be a syntax error is this code:
>
> def f():
>  a = 2
>  def g():
>    exec 'a = 42'
>    abc = a
>
> which throws syntax error.
>
> Cheers,
> fijal
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-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)