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

Steven Bethard steven.bethard at gmail.com
Sun Feb 26 18:17:31 CET 2006

On 2/25/06, Almann T. Goo <almann.goo at gmail.com> wrote:

On 2/23/06, Steven Bethard <steven.bethard at gmail.com> wrote: > On 2/22/06, Almann T. Goo <almann.goo at gmail.com> wrote: > > def incrementergetter(val): > > def incrementer(): > > val = 5 > > def inc(): > > ..val += 1 > > return val > > return inc > > return incrementer > > Sorry, what way did the user think? I'm not sure what you think was > supposed to happen.

My apologies ... I shouldn't use vague terms like what the "user thinks." My problem, as is demonstrated in the above example, is that the implicit nature of evaluating a name in Python conflicts with the explicit nature of the proposed "dot" notation. It makes it easier for a user to write obscure code (until Python 3K when we force users to use "dot" notation for all enclosing scope access ;-) ).

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 incrementer_getter(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 incrementer_getter().

STeVe

Grammar am for people who can't think for myself. --- Bucky Katt, Get Fuzzy

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