[Python-Dev] PEP for Better Control of Nested Lexical Scopes (original) (raw)

Almann T. Goo almann.goo at gmail.com
Tue Feb 21 16:12:06 CET 2006

But to the topic, it just occurred to me that any outer scopes could be given names (including global namespace, but that would have the name global by default, so global.x would essentially mean what globals()['x'] means now, except it would be a name error if x didn't pre-exist when accessed via namespacename.nameinspace notation.

namespace galias # galias.x becomes alternate spelling of global.x def outer(): namespace mezzanine a = 123 print a # => 123 print mezzanine.a # => 123 (the name space name is visible and functional locally) def inner(): print mezzanine.a => 123 mezznine.a =456 inner() print a # = 456 global.x = re-binds global x, name error if not preexisting. This would allow creating mezzanine like an attribute view of the slots in that local namespace, as well as making namespace itself visible there, so the access to mezzanine would look like a read access to an ordinary object named mezzanine that happened to have attribute slots matching outer's local name space.

This seems like a neat idea in principle, but I wonder if it removes consistency from the language. Consider that the scope that declares the namespace and its child scopes the names could be accessed by the namespace object or the direct name, but only in the child scopes can re-binding for the name be done via the namespace object.

def outer() : namespace n a = 5 # <-- same as n.a = 5 def inner() : print a # <-- same as n.a n.a = 7 # <-- not the same as a = 7 print n.a

I don't like how a child scope can access a free variable from an enclosing scope without the namespace object, but needs to use it for re-binding. Because of this, namespace objects have the potential to obfuscate things more than fix the language issue that I am addressing.

-Almann

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

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