[Python-Dev] Using and binding relative names (was Re: PEP for Better Control of Nested Lexical Scopes) (original) (raw)

Almann T. Goo almann.goo at gmail.com
Sun Feb 26 20:06:57 CET 2006

On 2/26/06, Steven Bethard <steven.bethard at gmail.com> wrote:

Then do you also dislike the original proposal: that only a single dot be allowed, and that the '.' would mean "this name, but in the nearest outer scope that defines it"? Then:

def incrementergetter(val): def incrementer(): val = 5 def inc(): .val += 1 return val return inc return incrementer would do what I think you want it to[1]. Note that I only suggested extending the dot-notation to allow multiple dots because of Greg Ewing's complaint that it wasn't enough like the relative import notation. Personally I find PJE's original proposal more intuitive, and based on your example, I suspect so do you. [1] That is, increment the val in incrementer(), return the same val, and never modify the val in incrementergetter().

I'm not sure if I find this more intuitive, but I think it is more convenient than the "explicit dots" for each scope. However my biggest issue is still there. I am not a big fan of letting users have synonyms for names. Notice how ".var" means the same as "var" in some contexts in the example above--that troubles me. PEP 227 addresses this concern with regard to the class scope:

Names in class scope are not accessible.  Names are resolved in
the innermost enclosing function scope.  If a class definition
occurs in a chain of nested scopes, the resolution process skips
class definitions.  This rule prevents odd interactions between
class attributes and local variable access.

As the PEP further states:

An alternative would have been to allow name binding in class
scope to behave exactly like name binding in function scope.  This
rule would allow class attributes to be referenced either via
attribute reference or simple name.  This option was ruled out
because it would have been inconsistent with all other forms of
class and instance attribute access, which always use attribute
references.  Code that used simple names would have been obscure.

I especially don't want to add an issue that is similar to one that PEP 227 went out of its way to avoid.

-Almann

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

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