Re: Objects in Python

References	(5 earlier) <mailman.3693.1345697563.4697.python-list@python.org> <5035d3e4$0$1645$c3e8da3$76491128@news.astraweb.com> <qotpq6irnjn.fsf@ruuvi.it.helsinki.fi> <mailman.3722.1345742227.4697.python-list@python.org> <50366ec8$0$6574$c3e8da3$5496439d@news.astraweb.com>
Date	2012-08-24 08:00 +1000
Subject	Re: Objects in Python
From	Chris Angelico <rosuav@gmail.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.3733.1345759262.4697.python-list@python.org> (permalink)

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On Fri, Aug 24, 2012 at 3:56 AM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> But name bindings are a kind of variable. Named memory locations are a
> *different* kind of variable. The behaviour of C variables and Python
> variables do not follow the Liskov Substitution Principle -- you can't
> rip out the entire "names bound to objects" machinery of Python and
> replace it with C-like named memory locations without changing the high-
> level behaviour of Python. And so by some ways of thinking it is *wrong*
> to treat name bindings and memory locations as "the same sort of entity".
> Hence, if C variables are variables, then Python name bindings can't be.

Yet Python's variables are extremely close to C's pointer variables.
If you allocate all your "real data" on the heap and do everything
with pointers, you'll have semantics very similar to Python's (except
that things aren't refcounted, so you have massive memory leaks). In
fact, that's how the Python-C API handles things - a PyObject*
basically _is_ a Python object, as far as C's concerned.

But again, that probably doesn't help explain the variables. Unless
you've come from (or can at least imagine) an environment in which you
use pointers for *everything*.

ChrisA

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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