Re: Objects in Python

From	Jussi Piitulainen <jpiitula@ling.helsinki.fi>
Newsgroups	comp.lang.python
Subject	Re: Objects in Python
Date	2012-08-23 11:59 +0300
Organization	University of Helsinki
Message-ID	<qotpq6irnjn.fsf@ruuvi.it.helsinki.fi> (permalink)
References	(2 earlier) <mailman.3668.1345654939.4697.python-list@python.org> <gsSdnaYuqqabhqjNnZ2dnUVZ8jmdnZ2d@bt.com> <87d32i1ntc.fsf@benfinney.id.au> <mailman.3693.1345697563.4697.python-list@python.org> <5035d3e4$0$1645$c3e8da3$76491128@news.astraweb.com>

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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).

It is very bad that people campaign here against the terminology that
is used in the official Python language reference and the Python
tutorial.

Best would be to simply explain how the variables, values, assignment,
and calls work in Python, the way the language reference and tutorial
actually do.

If the no-variables campaign is to continue, the language reference
and the tutorial should be changed to match. I would consider it a mad
move, but the current practice of badmouthing the official wording is
not healthy either.

> [...]
> > And many other languages have reference behavior and still call
> > their bindings "variables", e.g. Scheme.
> 
> Yes, well in my opinion, a great deal of the terminology in use is
> absolutely dire. E.g. both Ruby and Java have the exact same
> parameter binding strategy as Python, only the Ruby people call
> theirs "call by reference" and the Java people call theirs "call by
> value", *both of which are identical*, and NEITHER of which are the
> same thing that C and Pascal programmers will understand by call by
> value *or* call by reference.

That's indeed such a mess that those call-by-* terms may be now best
avoided. I would also avoid any distinction between an object and a
"reference" to an object, except as an implementation detail. It's not
helpful. It only leads to the confusion where it seems that Java (or
Python) does not actually have objects at all, only references to
objects, which in turn don't exist, so, er, what.

The swap function is helpful. Why doesn't it work? Because it assigns
to different variables that are local to the function. If I pass it a
list, why can it then swap the elements? Because that is the same
list, not a copy. Get used to it. Works for me.

Thread

Objects in Python shaun <shaun.wiseman91@gmail.com> - 2012-08-22 07:13 -0700
  Re: Objects in Python Joel Goldstick <joel.goldstick@gmail.com> - 2012-08-22 10:31 -0400
  Re: Objects in Python Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2012-08-22 17:31 +0300
  Re: Objects in Python Peter Otten <__peter__@web.de> - 2012-08-22 16:36 +0200
  Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-22 15:59 +0100
    Re: Objects in Python MRAB <python@mrabarnett.plus.com> - 2012-08-22 16:58 +0100
      Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-22 17:10 +0100
        Re: Objects in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-22 17:30 +0100
          Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-22 18:06 +0100
            Re: Objects in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-22 19:07 +0100
              Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-22 20:13 +0100
    Re: Objects in Python Terry Reedy <tjreedy@udel.edu> - 2012-08-22 13:01 -0400
      Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-22 18:46 +0100
        Re: Objects in Python Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-22 12:15 -0600
          Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-22 20:03 +0100
            Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-23 12:02 +1000
              Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-23 04:11 +0000
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-23 15:26 +1000
                Re: Objects in Python Jan Kuiken <jan.kuiken@quicknet.nl> - 2012-08-23 20:02 +0200
                Re: Objects in Python Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-23 12:17 -0600
                Re: Objects in Python Jan Kuiken <jan.kuiken@quicknet.nl> - 2012-08-23 22:43 +0200
                Re: Objects in Python 88888 Dihedral <dihedral88888@googlemail.com> - 2012-08-25 23:14 -0700
        Re: Objects in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-22 19:23 +0100
        Re: Re: Objects in Python Evan Driscoll <driscoll@cs.wisc.edu> - 2012-08-22 14:03 -0500
          Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-22 20:45 +0100
            Re: Objects in Python MRAB <python@mrabarnett.plus.com> - 2012-08-22 21:31 +0100
            Re: Objects in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-22 21:46 +0100
              Methods versus functions [was Re: Objects in Python] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-23 04:07 +0000
            Re: Re: Objects in Python Evan Driscoll <driscoll@cs.wisc.edu> - 2012-08-22 16:31 -0500
              Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-23 10:19 +0100
                Re: Re: Objects in Python Evan Driscoll <driscoll@cs.wisc.edu> - 2012-08-23 11:44 -0500
                Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-23 18:56 +0100
        Re: Objects in Python Ben Finney <ben+python@benfinney.id.au> - 2012-08-23 09:58 +1000
          Re: Objects in Python Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-22 18:10 -0600
          Re: Re: Objects in Python Evan Driscoll <driscoll@cs.wisc.edu> - 2012-08-22 23:49 -0500
            Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-23 06:55 +0000
              Re: Objects in Python Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2012-08-23 11:59 +0300
                Re: Objects in Python MRAB <python@mrabarnett.plus.com> - 2012-08-23 12:28 +0100
                Re: Objects in Python Jerry Hill <malaclypse2@gmail.com> - 2012-08-23 10:43 -0400
                Re: Objects in Python Evan Driscoll <driscoll@cs.wisc.edu> - 2012-08-23 12:17 -0500
                Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-23 17:56 +0000
                Variables vs names [was: Objects in Python] Evan Driscoll <driscoll@cs.wisc.edu> - 2012-08-23 14:22 -0500
                Re: Variables vs names Ben Finney <ben+python@benfinney.id.au> - 2012-08-24 10:02 +1000
                Re: Variables vs names [was: Objects in Python] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-25 02:05 +0000
                Re: Variables vs names Ben Finney <ben+python@benfinney.id.au> - 2012-08-25 15:24 +1000
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-24 08:00 +1000
                Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-25 03:04 +0000
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-25 16:34 +1000
                Re: Objects in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-25 09:55 +0100
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-25 20:23 +1000
                Re: Objects in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-25 12:01 +0100
                Re: Objects in Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-25 15:56 -0400
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-26 09:27 +1000
                Re: Objects in Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-25 20:43 -0400
                Re: Re: Objects in Python Evan Driscoll <driscoll@cs.wisc.edu> - 2012-08-26 00:25 -0500
                Re: Variables vs names [was: Objects in Python] Chris Angelico <rosuav@gmail.com> - 2012-08-24 09:34 +1000
                Re: Objects in Python Ben Finney <ben+python@benfinney.id.au> - 2012-08-24 09:49 +1000
                Re: Variables vs names [was: Objects in Python] Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-23 19:52 -0400
                Re: Objects in Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-23 19:54 -0400
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-24 10:01 +1000
                Re: Objects in Python Terry Reedy <tjreedy@udel.edu> - 2012-08-23 13:17 -0400
            Re: Objects in Python Ben Finney <ben+python@benfinney.id.au> - 2012-08-24 00:16 +1000
            Re: Objects in Python Roy Smith <roy@panix.com> - 2012-08-23 20:36 -0400
              Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-24 11:34 +1000
                Re: Objects in Python alex23 <wuwei23@gmail.com> - 2012-08-23 20:17 -0700
                Re: Re: Objects in Python Evan Driscoll <driscoll@cs.wisc.edu> - 2012-08-24 04:14 -0500
                Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-24 10:00 +0000
                Re: Objects in Python Grant Edwards <invalid@invalid.invalid> - 2012-08-24 13:27 +0000
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-25 05:18 +1000
                Re: Re: Objects in Python Evan Driscoll <driscoll@cs.wisc.edu> - 2012-08-26 00:45 -0500
                Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-26 13:43 +0000
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-26 23:58 +1000
                Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-26 14:18 +0000
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-27 00:54 +1000
                Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-26 22:47 +0000
                Re: Objects in Python Roy Smith <roy@panix.com> - 2012-08-26 10:02 -0400
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-27 00:14 +1000
                Re: Objects in Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-26 16:12 -0400
                Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-26 23:29 +0000
                Re: Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-26 16:22 +1000
                Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-26 12:02 +0000
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-26 23:34 +1000
                Re: Objects in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-26 15:02 +0100
                Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-27 00:05 +1000
                Re: Objects in Python Roy Smith <roy@panix.com> - 2012-08-26 09:41 -0400
              Identity function id() [was Re: Objects in Python] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-24 10:06 +0000
          Re: Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-23 15:33 +1000
          Re: Objects in Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-23 14:30 -0400
            Re: Objects in Python Alexander Blinne <news@blinne.net> - 2012-08-24 15:23 +0200
          Re: Objects in Python Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2012-08-24 09:38 +0200
          Re: Objects in Python Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2012-08-24 10:03 +0200
        Re: Objects in Python Walter Hurry <walterhurry@lavabit.com> - 2012-08-23 01:19 +0000
          Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-23 04:14 +0000
            Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-23 09:10 +0100
              Re: Objects in Python Ben Finney <ben+python@benfinney.id.au> - 2012-08-23 23:59 +1000
                Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-23 15:20 +0100
                Re: Objects in Python Ben Finney <ben+python@benfinney.id.au> - 2012-08-24 00:24 +1000
          Re: Objects in Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-23 09:03 +0100
        Re: Objects in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-23 04:34 +0000
          Re: Objects in Python rusi <rustompmody@gmail.com> - 2012-08-23 10:04 -0700
  Re: Objects in Python John Gordon <gordon@panix.com> - 2012-08-22 15:03 +0000
  Re: Objects in Python shaun <shaun.wiseman91@gmail.com> - 2012-08-22 08:25 -0700
    Re: Objects in Python Chris Angelico <rosuav@gmail.com> - 2012-08-23 01:47 +1000
    Re: Objects in Python Dave Angel <d@davea.name> - 2012-08-22 11:51 -0400
    Re: Objects in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-22 17:13 +0100
    Re: Objects in Python Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-22 11:29 -0600

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