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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: What other languages use the same data model as Python?
Date: Mon, 09 May 2011 16:23:21 -0400
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:5023

On 5/9/2011 10:29 AM, Steven D'Aprano wrote:
>
> If people then ask, how does the interpreter know the names?, I can add
> more detail: names are actually strings in a namespace, which is usually
> nothing more than a dict. Oh, and inside functions, it's a bit more
> complicated still. And so on.

Which is why I think it best to stick with 'A namespace is a many-to-one 
mapping (in other words, a function) of names to objects'. Any 
programmer should understand the abstractions 'mapping' and 'function'. 
Asking how the interpreter finds the object associated with a name 
amounts to asking how to do tabular lookup. Well, we basically know, 
though the details depends on the implementation of the table (mapping).

An interpreter can *implement* namespaces various ways. One is to 
objectify names and namespaces as strings and dicts. If the set of names 
in a namespace is fixed, another way is to objectify names and 
namespaces as ints and arrays. Python prohibits 'from x import *' within 
functions precisely to keep the set of local namespace names fixed. 
Therefore, CPython can and does always use C ints and array for function 
local namespaces.

-- 
Terry Jan Reedy