[Python-Dev] PEP for Better Control of Nested Lexical Scopes

[Almann T. Goo]

> Why not just use a class?
>
>
> def incgen(start=0, inc=1) :
>     class incrementer(object):
>       a = start - inc
>       def __call__(self):
>          self.a += inc
>          return self.a
>     return incrementer()
>
> a = incgen(7, 5)
> for n in range(10):
>     print a(),

Because I think that this is a workaround for a concept that the
language doesn't support elegantly with its lexically nested scopes.

IMO, you are emulating name rebinding in a closure by creating an
object to encapsulate the name you want to rebind--you don't need this
workaround if you only need to access free variables in an enclosing
scope.  I provided a "lighter" example that didn't need a callable
object but could use any mutable such as a list.

This kind of workaround is needed as soon as you want to re-bind a
parent scope's name, except in the case when the parent scope is the
global scope (since there is the "global" keyword to handle this). 
It's this dichotomy that concerns me, since it seems to be against the
elegance of Python--at least in my opinion.

It seems artificially limiting that enclosing scope name rebinds are
not provided for by the language especially since the behavior with
the global scope is not so.  In a nutshell I am proposing a solution
to make nested lexical scopes to be orthogonal with the global scope
and removing a "wart," as Jeremy put it, in the language.

-Almann

--
Almann T. Goo
almann.goo at gmail.com