namespace question

Steven D'Aprano steve+comp.lang.python at pearwood.info
Tue Feb 28 15:06:23 CET 2012


On Tue, 28 Feb 2012 22:36:56 +1100, Ben Finney wrote:

> Steven D'Aprano <steve+comp.lang.python at pearwood.info> writes:
> 
>> On Sun, 26 Feb 2012 19:47:49 +1100, Ben Finney wrote:
>>
>> >> An integer variable is a variable holding an integer. A string
>> >> variable is a variable holding a string. A list variable is a
>> >> variable holding a list.
>> > 
>> > And Python has none of those. Its references don't “hold” anything.
>>
>> Ah, but they do. Following the name binding:
>>
>> x = 1
>>
>> the name "x" now holds a reference to an int, or if you want to cut out
>> one layer of indirection, the name "x" holds an int. That is to say,
>> the value associated with the name "x" is an int.
> 
> Names don't hold anything. Not in natural language, and not in Python.

I don't agree, I think the analogy of "holding on to", or "holding", 
works well for names in this context. A *binding* (the term you prefer) 
refers to the process of *tying* two objects together with rope, string, 
or twine such that they *hold fast*. If names don't hold values, neither 
can they be bound.

I would be surprised if many programmers, whether experienced or not, or 
even non-programmers, failed to grasp the concept of a name "holding" a 
value. (And I point out that to *grasp a concept* is also to hold on to 
it. We hold our loved ones dear even when they are on the other side of 
the world, we hold these truths to be self-evident, and we don't hold 
with that sort of behaviour -- surely we are capable of holding onto the 
idea that names can hold values?)

But rather than spend any more time trying to convince you to hold a 
different opinion, I will accept your criticism and rephrase my earlier 
statement:

A string variable is a symbolic identifier given to a value and capable 
of being varied, which is given to a value which is a string.

Python has these -- it has names, which are symbolic identifiers given to 
values, and those name:value bindings are capable of varying. It has 
strings. And you can bind names to strings. Ergo, it has string variables.

I acknowledge that when I say "string variable", I mean a variable whose 
value is a string *at this moment*, I don't mean a variable which is 
prohibited by the compiler from taking a non-string value.

To the extent that careless use of the term variable may confuse the 
naive reader who assumes that Python is just like Pascal (or any other 
statically typed language), it is sometimes useful to emphasis the 
differences by talking about "name bindings". But sometimes it is useful 
to emphasis the similarities, in which case "name binding" is obfuscatory 
and "variable" is perfectly reasonable.



-- 
Steven



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