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

[Guido van Rossum]

[Jeremy]
>   >> The nested scopes rules don't kick in until you've got one
>   >> function nested in another.  The top-level namespace is treated
>   >> differently that other function namespaces.  If a function is
>   >> defined at the top-level then all its free variables are globals.
>   >> As a result, the old rules still apply.
> 
>   GvR> This doesn't make sense.  If the free variables were truely
>   GvR> considered globals, the reference to x would raise a NameError,
>   GvR> because the exec doesn't define it at the global level -- it
>   GvR> defines it at the local level.  So apparently you are
>   GvR> generating LOAD_NAME instead of LOAD_GLOBAL for free variables
>   GvR> in toplevel functions.  Oh well, this does the job!

[Jeremy]
> Actually, I only generate LOAD_NAME for unoptimized, top-level
> function namespaces.  These are exactly the old rules and I avoided
> changing them for top-level functions, except when they contained a
> nested function.

Aha.

> If we eliminate exec without "in," this is yet another problem that
> goes away.

But that's for another release...  That will probably get a lot of
resistance from some category of users!

So it's fine for now.  Thanks, Jeremy!  Great job!

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