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Groups > comp.lang.python > #67555
| From | Grant Edwards <invalid@invalid.invalid> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: Reference |
| Date | 2014-03-03 14:29 +0000 |
| Organization | PANIX Public Access Internet and UNIX, NYC |
| Message-ID | <lf23ki$ag5$2@reader1.panix.com> (permalink) |
| References | <53144e8d$0$2149$426a74cc@news.free.fr> |
On 2014-03-03, ast <nomail@invalid.com> wrote:
> hello
>
> Consider following code:
>
>>>> A=7
>>>> B=7
>>>> A is B
> True
>
> I understand that there is a single object 7 somewhere in memory
Maybe, maybe not. Integer are immutable, so that's allowed but not
required. In CPython, that's true for small integers, but that is an
implementation detail, and you shouldn't depend on it.
> and both variables A and B point toward this object 7
They might. They might not.
> now do the same with a list:
>
>>>> l1 = [1, 2]
>>>> l2 = [1, 2]
>>>> l1 is l2
> False
>
> It seems this time that there are 2 distincts objects [1, 2] in
> memory.
Yep. Lists are mutable, therefore each literal produces a distinct
object.
> l1 points toward the first one and l2 points toward the
> second one.
Yep.
> I dont really understand why the behavior is different.
> Both integer 7 and list [1, 2] are objects. Why is it
> different ?
Integer objects are immutable (they can't change value), therefore you
can reuse them without causing problems. Lists are mutable (you can
change the values in them), so you can't reuse them.
--
Grant Edwards grant.b.edwards Yow! Maybe I should have
at asked for my Neutron Bomb
gmail.com in PAISLEY --
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Reference "ast" <nomail@invalid.com> - 2014-03-03 10:42 +0100
Object identity (was: Reference) Ben Finney <ben+python@benfinney.id.au> - 2014-03-03 21:00 +1100
Re: Object identity (was: Reference) "ast" <nomail@invalid.com> - 2014-03-03 11:21 +0100
Re: Reference "Mark H. Harris" <harrismh777@gmail.com> - 2014-03-03 05:09 -0800
Re: Reference Grant Edwards <invalid@invalid.invalid> - 2014-03-03 14:29 +0000
Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-03 07:52 -0800
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 08:10 +1100
Re: Reference Tim Chase <python.list@tim.thechases.com> - 2014-03-03 15:24 -0600
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 08:31 +1100
Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-03 21:35 +0000
Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-04 00:07 +0200
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 09:18 +1100
Re: Reference Alister <alister.ware@ntlworld.com> - 2014-03-04 11:10 +0000
Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-04 11:48 +0000
Re: Reference "Rhodri James" <rhodri@wildebst.org.uk> - 2014-03-05 00:25 +0000
Re: Reference Tim Chase <python.list@tim.thechases.com> - 2014-03-03 15:51 -0600
Re: Reference Jerry Hill <malaclypse2@gmail.com> - 2014-03-03 17:02 -0500
Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-04 00:22 +0200
Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-04 09:27 +1100
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 09:33 +1100
Re: Reference Steven D'Aprano <steve@pearwood.info> - 2014-03-04 04:52 +0000
Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-04 16:24 +1100
Re: Reference "Rhodri James" <rhodri@wildebst.org.uk> - 2014-03-05 01:08 +0000
Re: Reference Roy Smith <roy@panix.com> - 2014-03-04 21:09 -0500
Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 19:36 -0800
Re: Reference Ian Kelly <ian.g.kelly@gmail.com> - 2014-03-04 21:08 -0700
Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 20:31 -0800
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-05 15:32 +1100
Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 20:47 -0800
Re: Reference Steven D'Aprano <steve@pearwood.info> - 2014-03-05 05:06 +0000
Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 21:47 -0800
Re: Reference alex23 <wuwei23@gmail.com> - 2014-03-05 16:01 +1000
Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 22:10 -0800
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-05 17:22 +1100
Re: Reference alex23 <wuwei23@gmail.com> - 2014-03-05 16:28 +1000
Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-05 12:24 +0000
Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-05 12:21 +0000
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-05 17:20 +1100
Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-05 09:40 -0800
Re: Reference Tim Chase <python.list@tim.thechases.com> - 2014-03-05 12:12 -0600
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 05:33 +1100
Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-05 18:19 +0000
Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 22:23 +0200
Re: Reference Grant Edwards <invalid@invalid.invalid> - 2014-03-05 20:31 +0000
Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 22:46 +0200
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 08:07 +1100
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 08:10 +1100
Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-05 21:34 +0000
Re: Reference Terry Reedy <tjreedy@udel.edu> - 2014-03-05 18:00 -0500
Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-06 03:01 +0000
Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 22:03 -0800
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-05 17:26 +1100
Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 17:32 +1100
Re: Reference Tim Chase <python.list@tim.thechases.com> - 2014-03-05 08:24 -0600
Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-05 18:29 +0000
Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 22:34 +0200
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 08:01 +1100
Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 23:14 +0200
Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-06 08:26 +1100
Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 23:50 +0200
Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-06 00:35 +0000
Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-06 11:50 +1100
Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-06 17:46 +0000
Re: Reference Tim Chase <python.list@tim.thechases.com> - 2014-03-05 15:33 -0600
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 08:37 +1100
Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-06 02:52 +0200
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 12:05 +1100
Re: Reference alex23 <wuwei23@gmail.com> - 2014-03-06 12:12 +1000
Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-05 21:46 +0000
Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 08:23 +0200
Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 22:33 -0800
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-05 17:40 +1100
Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-05 12:35 +0000
Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 23:45 +1100
Re: Reference Jerry Hill <malaclypse2@gmail.com> - 2014-03-04 10:19 -0500
Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-04 15:42 +0000
Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 03:02 +1100
Re: Reference Roy Smith <roy@panix.com> - 2014-03-04 11:14 -0500
Re: Reference MRAB <python@mrabarnett.plus.com> - 2014-03-04 17:12 +0000
Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 08:24 -0800
Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 02:25 +1100
Re: Reference Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2014-03-05 14:37 +0100
Re: Reference Steven D'Aprano <steve@pearwood.info> - 2014-03-04 03:59 +0000
Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 09:17 +1100
Re: Reference Roy Smith <roy@panix.com> - 2014-03-03 18:02 -0500
Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-04 10:09 +1100
Re: Reference Steven D'Aprano <steve@pearwood.info> - 2014-03-04 04:38 +0000
Re: Reference Terry Reedy <tjreedy@udel.edu> - 2014-03-03 13:48 -0500
Re: Reference Steven D'Aprano <steve@pearwood.info> - 2014-03-04 03:45 +0000
Re: Reference Alexander Blinne <news@blinne.net> - 2014-03-04 13:55 +0100
Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 01:06 +1100
Re: Reference Alexander Blinne <news@blinne.net> - 2014-03-04 22:53 +0100
Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 09:01 +1100
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