[Python-Dev] violently deprecating exec without in (was: nested scopes. global: have I got it right?)

[Guido van Rossum]

> >>>>> "SP" == Samuele Pedroni <pedroni@inf.ethz.ch> writes:
> 
>   SP> # top-level
>   SP> def g():
>   SP>   exec "x=3" 
>   SP>   return x
> 
> At the top-level, there is no closure created by the enclosing scope
> is not a function scope.  I believe that's the right thing to do,
> except that the exec "x=3" also assign to the global.
> 
> I'm not sure if there is a strong justification for allowing this
> form, except that it is the version of exec that is most likely to
> occur in legacy code.

Unfortunately this used to work, using a gross hack: when an exec (or
import *) was present inside a function, the namespace semantics *for
that function* was changed to the pre-0.9.1 semantics, where all names
are looked up *at run time* first in the locals then in the globals
and then in the builtins.

I don't know how common this is -- it's pretty fragile.  If there's a
great clamor, we can put this behavior back after b1 is released.

--Guido van Rossum (home page: http://www.python.org/~guido/)