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


Groups > comp.lang.python > #42155

Re: list comprehension misbehaving

Path csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!xlned.com!feeder7.xlned.com!news2.euro.net!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path <python-python-list@m.gmane.org>
X-Original-To python-list@python.org
Delivered-To python-list@mail.python.org
X-Spam-Status OK 0.020
X-Spam-Evidence '*H*': 0.96; '*S*': 0.00; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'subject:skip:c 10': 0.09; '"a"': 0.16; '-tkc': 0.16; 'loop.': 0.16; 'message-id:@post.gmane.org': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'tim,': 0.16; 'thanks,': 0.17; 'print': 0.22; 'header:User- Agent:1': 0.23; 'refers': 0.24; 'header:X-Complaints-To:1': 0.27; 'tim': 0.29; 'subject:list': 0.30; "i'm": 0.30; 'getting': 0.31; 'chase': 0.31; 'end,': 0.31; 'received:132': 0.31; 'writes:': 0.31; 'but': 0.35; 'charset:us-ascii': 0.36; 'thanks': 0.36; 'example,': 0.37; 'list': 0.37; 'to:addr:python-list': 0.38; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'middle': 0.60; "you're": 0.61; 'first': 0.61; 'skip:n 10': 0.64; 'taking': 0.65; 'results': 0.69; 'obvious.': 0.84; 'snapshot': 0.84
X-Injected-Via-Gmane http://gmane.org/
To python-list@python.org
From Wolfgang Maier <wolfgang.maier@biologie.uni-freiburg.de>
Subject Re: list comprehension misbehaving
Date Thu, 28 Mar 2013 15:52:29 +0000 (UTC)
References <loom.20130328T160914-263@post.gmane.org> <20130328104451.22bad9af@bigbox.christie.dr>
Mime-Version 1.0
Content-Type text/plain; charset=us-ascii
Content-Transfer-Encoding 7bit
X-Gmane-NNTP-Posting-Host sea.gmane.org
User-Agent Loom/3.14 (http://gmane.org/)
X-Loom-IP 132.230.1.31 (Mozilla/5.0 (Windows NT 6.1; rv:19.0) Gecko/20100101 Firefox/19.0)
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.3893.1364485979.2939.python-list@python.org> (permalink)
Lines 26
NNTP-Posting-Host 2001:888:2000:d::a6
X-Trace 1364485979 news.xs4all.nl 6899 [2001:888:2000:d::a6]:47672
X-Complaints-To abuse@xs4all.nl
Xref csiph.com comp.lang.python:42155

Show key headers only | View raw


Tim Chase <python.list <at> tim.thechases.com> writes:

> it's because you're taking a snapshot copy of "a" in the middle of
> the loop.  In your first example, if you change it to
> 
>   results = []
>   for i in a[:-1]:
>     results.append(a.pop() and a)
>   print results
> 
> you get the same thing as your list comprehension because each item
> in "results" refers to the now-(mostly)empty "a".
> 
> -tkc
> 
> 

Hi Tim, and thanks a lot for helping!
I got it:
in the comprehension case I'm only getting my results at the end,
when my list has been emptied!
Thanks, I got stuck with this, but now it's obvious.
Best,
Wolfgang

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


Thread

Re: list comprehension misbehaving Wolfgang Maier <wolfgang.maier@biologie.uni-freiburg.de> - 2013-03-28 15:52 +0000

csiph-web