Path: csiph.com!newsfeed.hal-mli.net!feeder3.hal-mli.net!newsfeed.hal-mli.net!feeder1.hal-mli.net!newsfeed.xs4all.nl!newsfeed4.news.xs4all.nl!xs4all!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 0.006 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'else:': 0.03; 'operator': 0.03; 'syntax': 0.04; 'clause': 0.09; 'false.': 0.09; 'parsing': 0.09; '(without': 0.16; 'from:addr:torriem': 0.16; 'from:name:michael torrie': 0.16; 'oddity': 0.16; 'slight': 0.16; 'subject:Case': 0.16; 'syntax,': 0.16; 'unlikely': 0.16; 'language': 0.16; 'wrote:': 0.18; 'code.': 0.18; 'normally': 0.19; '(in': 0.22; 'header:User-Agent:1': 0.23; 'adds': 0.24; 'equivalent': 0.26; 'header:In-Reply-To:1': 0.27; 'chris': 0.29; 'statement': 0.30; 'assumes': 0.31; 'block,': 0.31; 'comparison': 0.31; 'but': 0.35; 'really': 0.36; 'edge': 0.36; 'false': 0.36; 'keyword': 0.36; 'done': 0.36; 'message-id:@gmail.com': 0.38; 'to:addr:python-list': 0.38; 'pm,': 0.38; 'previous': 0.38; 'explain': 0.39; 'does': 0.39; 'though,': 0.39; 'to:addr:python.org': 0.39; 'enough': 0.39; 'either': 0.39; 'received:org': 0.40; 'easy': 0.60; 'expression': 0.60; 'skip:n 10': 0.64; 'effectively': 0.66; 'day': 0.76; "'case'": 0.84; 'opens': 0.91; 'subject:Proposal': 0.91 X-Virus-Scanned: amavisd-new at torriefamily.org Date: Sun, 06 Apr 2014 14:13:30 -0600 From: Michael Torrie User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131118 Thunderbird/17.0.11 MIME-Version: 1.0 To: python-list@python.org Subject: Re: Yet Another Switch-Case Syntax Proposal References: <8084-1396540962-768613@sneakemail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit 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: 35 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1396815239 news.xs4all.nl 2934 [2001:888:2000:d::a6]:33988 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:69781 On 04/06/2014 12:07 PM, Chris Angelico wrote: > This has a slight oddity of parsing (in that an expression can > normally have a comparison in it); if you really want to use the > result of a comparison inside a case block, you'd have to parenthesize > it. But it's easy enough to explain to a human. This syntax is almost identical to the if/elif/else syntax, though, no? > > case day in briefing_days: > lunch_time = datetime.time(11, 30) > meeting_time = datetime.time(12, 30) > case not in briefing_days + festive_days: > lunch_time = datetime.time(12) > meeting_time = datetime.time(14) > case in festive_days: > go_to_work = False > day_type = "festive" > else: > go_to_work = True > day_type = "ferial" > > A case statement that opens with a comparison operator takes the value > from the previous case (without re-evaluating it); a case statement > that lacks a comparison altogether assumes == and does the above. In > either case (pardon the pun), the check will be done only if the > preceding case was false. An 'else' clause is effectively equivalent > to a 'case' that's always true. > > Adds only one keyword to the language ("switch" is gone), and adds an > edge case to parsing that's unlikely to come up in non-contrived code. > > ChrisA >