Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #32911

Re: Multi-dimensional list initialization

Path csiph.com!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.xs4all.nl!newsfeed5.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
Return-Path <oscar.j.benjamin@gmail.com>
X-Original-To python-list@python.org
Delivered-To python-list@mail.python.org
X-Spam-Status OK 0.000
X-Spam-Evidence '*H*': 1.00; '*S*': 0.00; 'operator': 0.03; 'method.': 0.05; '[0]': 0.07; 'defines': 0.07; 'problem?': 0.07; 'repeated': 0.07; 'api': 0.09; '(although': 0.09; '[0,': 0.09; 'okay': 0.09; 'subclass': 0.09; 'subtle': 0.09; 'bug': 0.10; 'cc:addr:python-list': 0.10; 'thread': 0.11; 'library': 0.15; '(2,': 0.16; '0],': 0.16; '[2,': 0.16; 'backward': 0.16; 'benjamin': 0.16; 'cc:name:python list': 0.16; 'contrived': 0.16; 'expects': 0.16; 'general.': 0.16; 'input.': 0.16; 'losing': 0.16; 'wrote:': 0.17; 'passes': 0.17; 'tries': 0.17; '>>>': 0.18; 'subject:skip:i 10': 0.22; 'tuples': 0.22; 'cc:2**1': 0.24; 'least': 0.25; 'cc:addr:python.org': 0.25; 'header:In-Reply-To:1': 0.25; 'possibly': 0.27; 'message-id:@mail.gmail.com': 0.27; "doesn't": 0.28; 'subject:list': 0.28; 'objects': 0.29; 'received:209.85.215.46': 0.30; 'error': 0.30; 'gets': 0.32; 'problem.': 0.32; 'could': 0.32; 'hopefully': 0.33; 'problem': 0.33; 'agree': 0.34; 'received:google.com': 0.34; 'list': 0.35; 'adds': 0.35; 'described': 0.35; 'lists.': 0.35; 'said,': 0.35; 'expected': 0.35; 'received:209.85': 0.35; 'there': 0.35; 'but': 0.36; 'why': 0.37; 'received:209': 0.37; 'subject:: ': 0.38; 'mean': 0.38; 'object': 0.38; 'subject:-': 0.40; 'header:Received:5': 0.40; 'your': 0.60; 'different': 0.63; 'more': 0.63; 'sound': 0.65; 'absolutely': 0.84; 'oscar': 0.84
DKIM-Signature v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=B0yRi+lNI+SRXbRS0W2Xiw3pJcc7dNSUv1oy1ouHQWc=; b=s9OyWS1hWj6+aeUIQl2YUskxDNDWjfH1MFLu0KJF0Cpi0ZhO5Ef3fJsVFcHmll7+Yf NiY8zomq0QP9QxsDgqPRLsdhyQtQtPPtNFU10V6iOF7KD9lH1rSV5bnCnzr4233J25o1 ZmnPGV2Kzqqnqp1hj62Bpa0ZPmbDf6w2xbDBnMheNlh+irZ3c6bRBs6ItSsQEskGUqxS vQkgEuo8IO61fQ4OO2Ar9AXpsU0zIjKQtImpFr/yaJqB1abdj1b4It4HxDXXCxUvcnGO d6z7Mj0rlnmTlCWWQ/qZftZ+nAR1X8HUikacv7CPf4XYAotIZwUMR63IwsBBjauai8C/ PM3w==
MIME-Version 1.0
In-Reply-To <CAN1F8qUhgXM49jLq3GzJvdh86uy1VtdDBL1nupXsvO2f0DE5-Q@mail.gmail.com>
References <mailman.3267.1352096879.27098.python-list@python.org> <50978323$0$6908$e4fe514c@news2.news.xs4all.nl> <CAHVvXxQR2J2tyFcQZd7bNYTAeetwM+LfoV4UcYrkRfeNVOj+pg@mail.gmail.com> <CAPTjJmqzQi2TEjme_we-KfmG7vxOfRWoKG=zL=SGHYGqiFf9_Q@mail.gmail.com> <CAHVvXxQNCxpACM=tkKir0f3iVqui4oVGnyS-GywO+dtGacKAdQ@mail.gmail.com> <5098A55C.3090201@r3dsolutions.com> <CAPTjJmpjwNtn-Dj2vyP2CPt+BZUzBgCkCvG=3J=x5=2ftmV04A@mail.gmail.com> <5098C873.2000200@r3dsolutions.com> <CALwzidmx0HxJ9-2GkzPWMV5VCKc+ypOp8D2qSxw-MfmyS9No1Q@mail.gmail.com> <509982CA.7050701@r3dsolutions.com> <mailman.3342.1352242045.27098.python-list@python.org> <afua6hFbj9gU2@mid.individual.net> <CAHVvXxQMe9zR074gCcXwJ7W_f_eDF6Lqk8MsbBn-hRgkHAXPzg@mail.gmail.com> <CAN1F8qXn2cesoHyBq1dyp8QYGB-Cir13eC5PtYW+m-WDXzmyhw@mail.gmail.com> <CAHVvXxRX0Xa9J0HSnGYfsd+gxbXBoFx5etm7B=A7GkHs3aRVVg@mail.gmail.com> <CAN1F8qUhgXM49jLq3GzJvdh86uy1VtdDBL1nupXsvO2f0DE5-Q@mail.gmail.com>
Date Wed, 7 Nov 2012 23:06:27 +0000
Subject Re: Multi-dimensional list initialization
From Oscar Benjamin <oscar.j.benjamin@gmail.com>
To Joshua Landau <joshua.landau.ws@gmail.com>
Content-Type text/plain; charset=ISO-8859-1
Cc Python List <python-list@python.org>, Gregory Ewing <greg.ewing@canterbury.ac.nz>
X-BeenThere python-list@python.org
X-Mailman-Version 2.1.15
Precedence list
List-Id General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe <http://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive <http://mail.python.org/pipermail/python-list/>
List-Post <mailto:python-list@python.org>
List-Help <mailto:python-list-request@python.org?subject=help>
List-Subscribe <http://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups comp.lang.python
Message-ID <mailman.3399.1352329595.27098.python-list@python.org> (permalink)
Lines 41
NNTP-Posting-Host 2001:888:2000:d::a6
X-Trace 1352329595 news.xs4all.nl 6905 [2001:888:2000:d::a6]:55763
X-Complaints-To abuse@xs4all.nl
Xref csiph.com comp.lang.python:32911

Show key headers only | View raw

On 7 November 2012 22:16, Joshua Landau <joshua.landau.ws@gmail.com> wrote:
> On 7 November 2012 14:00, Oscar Benjamin <oscar.j.benjamin@gmail.com> wrote:
>> On 7 November 2012 13:39, Joshua Landau <joshua.landau.ws@gmail.com>
>> wrote:
>> > On 7 November 2012 11:11, Oscar Benjamin <oscar.j.benjamin@gmail.com>
>> > wrote:
>> >> A more modest addition for the limited case described in this thread
>> >> could
>> >> be to use exponentiation:
>> >>
>> >> >>> [0] ** (2, 3)
>> >> [[0, 0, 0], [0, 0, 0]]
>>
>> Exponentiation is expected to be asymmetric and is currently unused so
>> there is no ambiguity. The problem is if someone has already
>> subclassed list and added an exponentiation method.
>
> How is that a problem? They just wont get the functionality.

This is absolutely contrived but:
Library A defines a subclass of list that adds an exponentiation
operator thinking that it's okay to still use these objects as lists.
Library B has an API that expects a list and tries to use the list
copy-exponentiation on its input. A user passes a list type object
from library A into library B and hopefully gets an error but possibly
gets a subtle bug that is hard to track down.

It doesn't sound plausible to me but at least in principle there is a
backward compatibility problem.

> That said, losing:
> [0] * (2, 3) == [0] * [2, 3]
> would mean losing duck-typing in general. *Thus*, I fully agree with your
> choice of exponentiation.

Also there's no reason why tuples couldn't have the same
exponentiation operator (although for them it would be no different
from repeated multiplication).


Oscar

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Multi-dimensional list initialization Demian Brecht <demianbrecht@gmail.com> - 2012-11-04 22:27 -0800
  Re: Multi-dimensional list initialization Hans Mulder <hansmu@xs4all.nl> - 2012-11-05 10:13 +0100
    Re: Multi-dimensional list initialization Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-11-06 01:32 +0000
    Re: Multi-dimensional list initialization Chris Angelico <rosuav@gmail.com> - 2012-11-06 13:01 +1100
    Re: Multi-dimensional list initialization Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-11-06 02:30 +0000
    Re: Multi-dimensional list initialization Andrew Robinson <andrew3@r3dsolutions.com> - 2012-11-05 21:51 -0800
      Re: Multi-dimensional list initialization Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-06 09:04 +0000
        RE: Multi-dimensional list initialization "Shambhu Rajak" <shambhu.rajak@calsoftinc.com> - 2012-11-06 18:57 +0530
        Re: Multi-dimensional list initialization Andrew Robinson <andrew3@r3dsolutions.com> - 2012-11-06 14:41 -0800
          Re: Multi-dimensional list initialization Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-07 01:55 +0000
            Re: Multi-dimensional list initialization Demian Brecht <demianbrecht@gmail.com> - 2012-11-06 22:56 -0800
            Re: Multi-dimensional list initialization wxjmfauth@gmail.com - 2012-11-07 00:57 -0800
            Re: Multi-dimensional list initialization Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-11-07 22:27 +0000
            Re: Multi-dimensional list initialization Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-07 16:39 -0700
            Re: Multi-dimensional list initialization Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-08 00:09 -0700
            Re: Multi-dimensional list initialization Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-08 08:58 -0700
            Re: Multi-dimensional list initialization Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-11-09 01:39 +0000
            Re: Multi-dimensional list initialization Chris Angelico <rosuav@gmail.com> - 2012-11-09 17:07 +1100
              Re: Multi-dimensional list initialization Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-09 06:37 +0000
                Re: Multi-dimensional list initialization Chris Angelico <rosuav@gmail.com> - 2012-11-09 17:59 +1100
                Re: Multi-dimensional list initialization Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-11-09 07:27 +0000
                Re: Multi-dimensional list initialization rusi <rustompmody@gmail.com> - 2012-11-09 07:05 -0800
                Re: Multi-dimensional list initialization Chris Angelico <rosuav@gmail.com> - 2012-11-10 02:23 +1100
            Re: Multi-dimensional list initialization Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-11-09 14:34 -0500
            RE: Multi-dimensional list initialization "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-11-09 20:31 +0000
            Re: Multi-dimensional list initialization Ethan Furman <ethan@stoneleaf.us> - 2012-11-09 13:49 -0800
        RE: Multi-dimensional list initialization "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-11-06 23:39 +0000
        Re: Multi-dimensional list initialization Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-06 16:52 -0700
        Re: Multi-dimensional list initialization MRAB <python@mrabarnett.plus.com> - 2012-11-07 00:23 +0000
          Re: Multi-dimensional list initialization rusi <rustompmody@gmail.com> - 2012-11-06 20:11 -0800
          Re: Multi-dimensional list initialization Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-07 05:05 +0000
            Re: Multi-dimensional list initialization Roy Smith <roy@panix.com> - 2012-11-07 00:12 -0500
              Re: Multi-dimensional list initialization Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2012-11-07 18:32 +1300
                RE: Multi-dimensional list initialization "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-11-07 15:57 +0000
            Re: Multi-dimensional list initialization Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2012-11-07 10:52 +0200
            Re: Multi-dimensional list initialization MRAB <python@mrabarnett.plus.com> - 2012-11-07 17:17 +0000
              Re: Multi-dimensional list initialization Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-07 22:36 +0000
        Re: Multi-dimensional list initialization Ethan Furman <ethan@stoneleaf.us> - 2012-11-07 07:23 -0800
        Re: Multi-dimensional list initialization Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-07 14:01 -0700
          Re: Multi-dimensional list initialization Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-08 00:00 +0000
            Re: Multi-dimensional list initialization Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-11-08 00:30 +0000
              Re: Multi-dimensional list initialization Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-08 03:47 +0000
            Re: Multi-dimensional list initialization Andrew Robinson <andrew3@r3dsolutions.com> - 2012-11-07 20:51 -0800
            Re: Multi-dimensional list initialization wrw@mac.com - 2012-11-08 08:26 -0500
        Re: Multi-dimensional list initialization Andrew Robinson <andrew3@r3dsolutions.com> - 2012-11-07 16:24 -0800
          Re: Multi-dimensional list initialization Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-08 04:20 +0000
    Re: Multi-dimensional list initialization Chris Angelico <rosuav@gmail.com> - 2012-11-06 17:07 +1100
    Re: Multi-dimensional list initialization Andrew Robinson <andrew3@r3dsolutions.com> - 2012-11-06 00:21 -0800
    Re: Multi-dimensional list initialization Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-06 02:19 -0700
    RE: Multi-dimensional list initialization "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-11-06 17:32 +0000
    Re: Multi-dimensional list initialization Andrew Robinson <andrew3@r3dsolutions.com> - 2012-11-06 13:14 -0800
    Re: Multi-dimensional list initialization Andrew Robinson <andrew3@r3dsolutions.com> - 2012-11-06 13:19 -0800
    Re: Multi-dimensional list initialization Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-06 15:46 -0700
      Re: Multi-dimensional list initialization Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2012-11-07 18:34 +1300
        Re: Multi-dimensional list initialization Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-11-07 14:00 +0000
        Re: Multi-dimensional list initialization Ethan Furman <ethan@stoneleaf.us> - 2012-11-07 06:47 -0800
        Re: Multi-dimensional list initialization Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-11-07 23:06 +0000
        Re: Multi-dimensional list initialization Greg Ewing <greg.ewing@canterbury.ac.nz> - 2012-11-08 14:29 +1300
  Re: Multi-dimensional list initialization wxjmfauth@gmail.com - 2012-11-05 01:55 -0800

csiph-web