Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.xs4all.nl!newsfeed3a.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 0.005 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'syntax': 0.04; 'anyway.': 0.05; 'root': 0.05; 'tries': 0.07; 'string': 0.09; 'agree,': 0.09; 'feature,': 0.09; 'forcing': 0.09; 'prefix': 0.09; 'semantic': 0.09; 'cc:addr:python-list': 0.11; 'python': 0.11; 'advantage.': 0.16; 'codebases.': 0.16; 'from:addr:rosuav': 0.16; 'from:name:chris angelico': 0.16; 'ideally,': 0.16; 'oppose': 0.16; 'portable': 0.16; 'simpson': 0.16; 'exception': 0.16; 'fix': 0.17; 'wrote:': 0.18; 'trying': 0.19; 'code,': 0.22; 'example': 0.22; 'cc:addr:python.org': 0.22; 'unicode': 0.24; 'cc:2**0': 0.24; 'header:In-Reply-To:1': 0.27; 'point': 0.28; 'chris': 0.29; 'am,': 0.29; 'then.': 0.30; 'message-id:@mail.gmail.com': 0.30; 'code': 0.31; '(usually': 0.31; 'exceptions': 0.31; 'routine': 0.31; 'class': 0.32; 'this.': 0.32; 'run': 0.32; 'guess': 0.33; 'could': 0.34; 'subject:with': 0.35; "can't": 0.35; 'common': 0.35; 'but': 0.35; 'received:google.com': 0.35; 'add': 0.35; 'there': 0.35; "i'll": 0.36; 'bringing': 0.38; 'that,': 0.38; 'recent': 0.39; 'does': 0.39; '12,': 0.39; 'how': 0.40; 'remove': 0.60; 'catch': 0.60; 'serving': 0.60; 'truly': 0.60; "you're": 0.61; "you'll": 0.62; 'believe': 0.68; '*and*': 0.84; '2015': 0.84; 'confusing': 0.84; 'everything,': 0.84; 'everything.': 0.84; 'noise': 0.84; 'subject:..': 0.84; 'absolutely': 0.87; 'why?': 0.91; 'to:none': 0.92 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:cc :content-type; bh=jTRix//b/S8IpZ6AQIG/R9KV5Fb2NQCf/Mr/ZcmuSzc=; b=rn31UJ4bSYi6Qw4uu8QPo73lfGVECT4NrtHkOfJ8czGJIUPDsIALnLp1ZvKg94NYOD zQatIOizQ+DSvCeyduOOaPQvp2kzJDTI9q6eERE7n5cEZXPt/IZ5y2npOOg2h+IPwwHN SrjuaR7G+4zd6eFVERKKWBlHCBOyDoqvg7kEz+Ak1KlXd3YuNclXIe0JKher8Bo6rY3J y3XHShL3Xne/dJvhYuYDnZJmqeS2XiTSkQ7RDMr8p27G/KrMGJ0X9rJ3ehqtM1FmBwNK evVksx7++vW6TQkV9+HI4VWZXRjYWqbM8fRN+De1GFo4RgXLrtyPh9kfWlkOsOOaX1Ra UhEA== MIME-Version: 1.0 X-Received: by 10.42.50.134 with SMTP id a6mr11156285icg.12.1428789171522; Sat, 11 Apr 2015 14:52:51 -0700 (PDT) In-Reply-To: <20150411213734.GA78999@cskk.homeip.net> References: <20150411213734.GA78999@cskk.homeip.net> Date: Sun, 12 Apr 2015 07:52:51 +1000 Subject: Re: try..except with empty exceptions From: Chris Angelico Cc: "python-list@python.org" Content-Type: text/plain; charset=UTF-8 X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.20 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: 36 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1428789174 news.xs4all.nl 2907 [2001:888:2000:d::a6]:33133 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:88844 On Sun, Apr 12, 2015 at 7:37 AM, Cameron Simpson wrote: > On 11Apr2015 21:21, Chris Angelico wrote: >> >> But I agree, it would be very nice if Python 3 could have abolished >> the truly confusing part of this, where "except:" catches everything. >> Forcing people to spell it "except BaseException:" would fix all of >> this. How hard is it to deprecate and then remove that, same as string >> exceptions were removed? > > > I guess I'll go over there to oppose it then. > > Why? It makes it harder to write portable python 2/3 code and does not add > any semantic advantage. > > Unless there's a common root exception class in Python 2, which I believe > there isn't, you can't catch all exceptions in python 2 without the > "except:" syntax. Which means the _only_ way to have some code in both 2 > and 3 that does it requires 2 codebases. > > As one who tries to have his code run in both 2 (usually recent 2, like > 2.6/2.7) and 3, this change would cause a signification breakage for me > without bringing any semantic benefits. Can you give an example of a place where in Py2 you absolutely have to catch everything, and don't have control over the code, *and* are trying to do a one-codebase routine with Py3 compatibility? If you're trying for 2/3 compatibility, you'll need to have all your exceptions derive from BaseException anyway. At very worst, it could be turned into a compat-only syntax feature, like the u"spam" noise prefix on Unicode strings - serving absolutely no purpose in Py3 code, and ideally, able to be removed at some point post-2020. ChrisA