Path: csiph.com!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder1.enfer-du-nord.net!feeds.phibee-telecom.net!newsfeed.xs4all.nl!newsfeed4.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
Return-Path: <rosuav@gmail.com>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.041
X-Spam-Evidence: '*H*': 0.92; '*S*': 0.00; 'subject:two': 0.07; '[1,': 0.09; 'subject:into': 0.09; 'sure,': 0.09; 'thrown': 0.09; 'ah,': 0.16; 'algorithmic': 0.16; 'from:addr:rosuav': 0.16; 'from:name:chris angelico': 0.16; 'hmm.': 0.16; 'low.': 0.16; 'roy': 0.16; 'subject:based': 0.16; 'there...': 0.16; 'uniquely': 0.16; 'wrote:': 0.18; 'wed,': 0.18; 'meant': 0.20; '>>>': 0.22; 'affects': 0.24; 'header:In-Reply-To:1': 0.27; 'chris': 0.29; 'am,': 0.29; 'forgot': 0.30; 'relative': 0.30; 'subject:list': 0.30; 'message-id:@mail.gmail.com': 0.30; 'getting': 0.31; '>>>>': 0.31; 'another': 0.32; 'case,': 0.35; 'but': 0.35; 'received:google.com': 0.35; 'subject:?': 0.36; 'skip:o 20': 0.38; '8bit%:86': 0.38; 'skip:[ 10': 0.38; 'to:addr:python-list': 0.38; 'list,': 0.38; '12,': 0.39; 'to:addr:python.org': 0.39; 'numbers': 0.61; 'complete': 0.62; 'costs': 0.63; 'smith': 0.68; 'fail.': 0.84; 'no:': 0.84; 'otten': 0.84; 'ridiculously': 0.84; 'absolutely': 0.87; 'notion': 0.91; 'songs': 0.91; 'choice.': 0.93; '2013': 0.98
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 :content-type:content-transfer-encoding; bh=1/gD+6kvOey2DJj9wWKoTeet6czITClckxG86s1FBrE=; b=GHEgTNsIhM7ctvq1tfvwugY69/TmQhP7+wDaGdiqoQtfr9ONlfqGVdCM2ihwuRvtDy nvwaPeGiKal6axKZqEGphSfOAYWdhRm0lOYaQ3XkMf6avn44q8/YcbB20iEOxV0arsCt WZcW8NQP65cxgVAYkNP1d6WpmVjNDHdMH+YWIORTVcphX3WDK42+w9OsFKzxt4lOYTq7 dMtgUOeA3kgb898YVVyeSOQO4+h+O2RXIFLqL/JHOE4xcXNBF6y7SHzYl7j9gTqvWH++ tSnN6uTEuaEGY7xbUuPwXTyqi3FoOKf8xY8FwicoM+greZfI35Ozxo7/jgJ8AsGDgmBy soig==
MIME-Version: 1.0
X-Received: by 10.52.117.16 with SMTP id ka16mr7019260vdb.43.1370975221770; Tue, 11 Jun 2013 11:27:01 -0700 (PDT)
In-Reply-To: <kp7pk1$2i7$1@ger.gmane.org>
References: <kp5d9e$2hf$1@panix2.panix.com> <CAPTjJmrDNe8ASxD8xsok=-_zoDRrUZjHydYSm3G_SJy8T2a_5A@mail.gmail.com> <kp7fmp$es8$2@ger.gmane.org> <CAPTjJmqJftDD8zjW9NZen=61ePD8Tuf1Rsph9K+kmJpNd=ZmEw@mail.gmail.com> <kp7pk1$2i7$1@ger.gmane.org>
Date: Wed, 12 Jun 2013 04:27:01 +1000
Subject: Re: Split a list into two parts based on a filter?
From: Chris Angelico <rosuav@gmail.com>
To: python-list@python.org
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
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.3038.1370975224.3114.python-list@python.org>
Lines: 47
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1370975224 news.xs4all.nl 15969 [2001:888:2000:d::a6]:56024
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:47694

On Wed, Jun 12, 2013 at 4:13 AM, Peter Otten <__peter__@web.de> wrote:
> Chris Angelico wrote:
>
>> On Wed, Jun 12, 2013 at 1:28 AM, Serhiy Storchaka <storchaka@gmail.com>
>> wrote:
>>> 11.06.13 01:50, Chris Angelico =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=
=B2(=D0=BB=D0=B0):
>>>
>>>> On Tue, Jun 11, 2013 at 6:34 AM, Roy Smith <roy@panix.com> wrote:
>>>>>
>>>>> new_songs =3D [s for s in songs if s.is_new()]
>>>>> old_songs =3D [s for s in songs if not s.is_new()]
>>>>
>>>>
>>>> Hmm. Would this serve?
>>>>
>>>> old_songs =3D songs[:]
>>>> new_songs =3D [songs.remove(s) or s for s in songs if s.is_new()]
>
> I think you meant old_songs.remove(s).

Ah, yes, editing fail. I started by mutating the original list, then
thought "Oh, better to work with a copy"... and forgot to complete the
edit.

>>> O(len(songs)**2) complexity.
>>
>> Which isn't significant if len(songs) is low. We weren't told the
>> relative costs - is the is_new call ridiculously expensive? Everything
>> affects algorithmic choice.
>
> But is it correct? In the general case, no:
>
>>>> numbers =3D [1, 1.0, 2.0, 2]
>>>> ints =3D numbers[:]
>>>> floats =3D [ints.remove(n) or n for n in numbers if isinstance(n, floa=
t)]
>>>> floats
> [1.0, 2.0]
>>>> ints
> [1.0, 2] # hmm

Sure, but the implication of the original is that they're uniquely
identifiable. Anyway, it wasn't meant to be absolutely perfect, just
another notion getting thrown out there... and then thrown out :)

ChrisA