Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!rt.uk.eu.org!newsfeed.xs4all.nl!newsfeed2.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; 'syntax': 0.04; 'assignment': 0.07; 'class,': 0.07; 'nicely': 0.07; 'consistency': 0.09; 'inserted': 0.09; 'lawrence': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'rejected': 0.09; 'python': 0.11; 'jan': 0.12; 'assignments': 0.16; 'c/c++': 0.16; 'ought': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'reedy': 0.16; 'suggestion.': 0.16; 'target"': 0.16; 'wrote:': 0.18; '>>>': 0.22; 'appears': 0.22; 'header:User-Agent:1': 0.23; 'source': 0.25; 'possibly': 0.26; 'suggested': 0.26; 'post': 0.26; 'least': 0.26; 'header:X -Complaints-To:1': 0.27; 'header:In-Reply-To:1': 0.27; 'point': 0.28; 'testing': 0.29; 'character': 0.29; 'end,': 0.31; 'equality': 0.31; 'gary': 0.31; 'occurs': 0.31; 'post.': 0.31; 'workaround': 0.31; 'another': 0.32; 'quite': 0.32; 'style': 0.33; 'something': 0.35; 'but': 0.35; 'there': 0.35; 'whilst': 0.36; 'example,': 0.37; 'follows:': 0.38; 'to:addr:python-list': 0.38; 'pm,': 0.38; 'rather': 0.38; 'that,': 0.38; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'easy': 0.60; 'liked': 0.60; 'john': 0.61; 'received:173': 0.61; 'further': 0.61; 'different': 0.65; 'here': 0.66; 'between': 0.67; 'advantages': 0.68; 'apart': 0.72; "'with'": 0.84; 'avoids': 0.84; 'received:fios.verizon.net': 0.84; 'sorry.': 0.91 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Terry Reedy Subject: Re: Ifs and assignments Date: Fri, 03 Jan 2014 03:53:53 -0500 References: <52C59FF6.5000607@allsup.co> <52C5BD90.9020609@islandtraining.com> <52C5DDA6.5090207@allsup.co> <52C60AF6.8060004@islandtraining.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Gmane-NNTP-Posting-Host: pool-173-75-254-207.phlapa.fios.verizon.net User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 In-Reply-To: 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: 51 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1388739253 news.xs4all.nl 2858 [2001:888:2000:d::a6]:33438 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:63041 On 1/2/2014 8:20 PM, Mark Lawrence wrote: > On 03/01/2014 00:57, Gary Herron wrote: >> On 01/02/2014 01:44 PM, John Allsup wrote: >>> The point of my original post was that, whilst C's >>> if( x = 2 ) { do something } >>> and >>> if( x == 2 ) { do something } >>> are easy to confuse, and a source of bugs, having a construct like >>> follows: >>> >>> if x == 2: >>> do something # what happens at present >>> if testFunc() as x: >>> do something with x >>> >>> using the 'as' syntax that appears with 'with' and 'except', would allow >>> for the advantages of C style assignments in conditionals but without >>> the easy confusion, since here the syntax is significantly different >>> between assignment and equality testing (rather than a character apart >>> as happens with C). >>> >>> This occurs further down in my original post (past the point where you >>> inserted your reply). >>> >>> Another post suggested a workaround by defining a 'pocket' class, for >>> which I am grateful. >>> >>> John >> >> Sorry. I shot off my answer before reading the whole post. That's >> never a good idea. >> >> >> After reading to the end, I rather like your suggestion. It works well >> in your example, , nicely avoids the C/C++ trap, and has some >> consistency with other parts of Python. >> >> Gary Herron >> >> > > I liked the look of this as well. It ought to go to python ideas, or > has it been suggested there in the past? Yes, and rejected (I am quite sure). Consistency would 'demand' at least "while expr as target" and possibly "for i in iterable_expr as target". -- Terry Jan Reedy