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Date: Thu, 23 Aug 2012 12:28:55 +0100
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Subject: Re: Objects in Python
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Xref: csiph.com comp.lang.python:27726

On 23/08/2012 09:59, Jussi Piitulainen wrote:
> Steven D'Aprano writes:
>> On Wed, 22 Aug 2012 23:49:17 -0500, Evan Driscoll wrote:
>>
>> > On 8/22/2012 18:58, Ben Finney wrote:
>> >> You haven't discovered anything about types; what you have
>> >> discovered is that Python name bindings are not variables.
>> >>
>> >> In fact, Python doesn't have variables – not as C or Java
>> >> programmers would understand the term. What it has instead are
>> >> references to objects (with names as one kind of reference).
>> >
>> > OK, I've seen this said a few times, and I have to ask: what do
>> > you mean by this? I consider myself pretty decent at Python and
>> > other languages, and I really don't get it.
>>
>> I think the point that Ben would like to make is that while "name
>> binding" is a specific kind of "variable", the word "variable" comes
>> with too much baggage from the old-school C, Pascal etc. style of
>> variables- are-named-memory-locations. Most of the time, the
>> differences are unimportant, but when they are important, if your
>> mental image is that Python "variables" (name bindings) are like C
>> or Pascal "variables" (memory locations), you're going to get
>> confused.
>
> I don't get it either. To me the python-has-no-variables campaigners
> seem confused. As far as I can see, Python can be seen in terms of
> variables bound to (locations containing) values perfectly well, in a
> way that should be quite familiar to people who come from Java (or
> Lisp, Scheme like me).
>
[snip]
In Java a variable exists even when it has not been assigned a value.
In Python, on the other hand, the basic model is that a 'variable'
doesn't exist until it has been bound to an value (although, for
efficiency reasons, that's not entirely true, because at compile time
CPython will identify the local variables in a function and allocate a
'slot' for it).