Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!feeder.erje.net!eu.feeder.erje.net!xlned.com!feeder5.xlned.com!newsfeed.xs4all.nl!newsfeed3.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.001 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'python.': 0.02; 'subject:Python': 0.06; 'context': 0.07; 'indexing': 0.07; 'list?': 0.07; 'none,': 0.07; 'false,': 0.09; 'from:addr:ethan': 0.09; 'from:addr:stoneleaf.us': 0.09; 'from:name:ethan furman': 0.09; 'message-id:@stoneleaf.us': 0.09; '~ethan~': 0.09; 'bug': 0.12; 'posted': 0.15; 'empty,': 0.16; 'fine.': 0.16; 'reedy': 0.16; 'slice.': 0.16; 'index': 0.16; 'wrote:': 0.18; '>>>': 0.22; 'header:User-Agent:1': 0.23; 'instance,': 0.24; 'specifies': 0.24; 'header:In-Reply-To:1': 0.27; 'chris': 0.29; 'am,': 0.29; 'statement': 0.30; "i'm": 0.30; 'program,': 0.31; '>>>>': 0.31; 'crash': 0.31; 'languages': 0.32; 'another': 0.32; 'everyone': 0.33; 'ago': 0.33; 'but': 0.35; 'really': 0.36; 'charset:us- ascii': 0.36; 'list': 0.37; 'list.': 0.37; 'expected': 0.38; 'sometimes': 0.38; 'to:addr:python-list': 0.38; 'pm,': 0.38; 'to:addr:python.org': 0.39; 'most': 0.60; 'received:173': 0.61; 'further': 0.61; 'skip:n 10': 0.64; 'received:69.56': 0.68; 'obvious': 0.74; 'ethan': 0.84; 'furman': 0.84; 'received:69.56.148': 0.84; 'received:gateway15.websitewelcome.com': 0.84; 'trick,': 0.84 Date: Thu, 10 Oct 2013 19:47:02 -0700 From: Ethan Furman User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121010 Thunderbird/16.0.1 MIME-Version: 1.0 To: python-list@python.org Subject: Re: Python's and and Pythons or References: <91180c35-413f-4b65-a224-917d8d68b7ec@googlegroups.com> <5256ACAB.7050809@stoneleaf.us> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator3304.hostgator.com X-AntiAbuse: Original Domain - python.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - stoneleaf.us X-BWhitelist: no X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: ([173.12.184.233]) [173.12.184.233]:51093 X-Source-Auth: ethan+stoneleaf.us X-Email-Count: 1 X-Source-Cap: dG9idWs7dG9idWs7Z2F0b3IzMzA0Lmhvc3RnYXRvci5jb20= X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 27 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1381459623 news.xs4all.nl 15884 [2001:888:2000:d::a6]:59220 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:56636 On 10/10/2013 06:41 PM, Terry Reedy wrote: > On 10/10/2013 9:33 AM, Ethan Furman wrote: > >> On 10/10/2013 12:43 AM, Terry Reedy wrote: > >>> On 10/10/2013 2:45 AM, Chris Angelico wrote: >>>> first_element = some_list[0] # Oops, may crash > >>> some_list[0:1] always works, and sometimes is usable, but you still >>> cannot index the slice. > >> Not if some_list is None, False, or another non-indexable type. > > Did you really not understand that some_list is intended to be a list? Just like my_string, for instance, would be a > string? Chris's statement further specifies some_list as a list that is expected to not be empty, but might be -- so one > has to guard against the possibility. I understood it just fine. I'm also aware that at some point, in some program, it will be None (and it won't be a bug ;). > The trick of slicing instead of indexing in this context is not obvious to everyone learning Python. Most other > languages only have indexing. I learned the trick years ago when someone posted it on this list. It's a good trick, I use it myself. -- ~Ethan~