Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!rt.uk.eu.org!newsfeed.xs4all.nl!newsfeed2a.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 0.000 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; '(at': 0.04; 'warnings': 0.04; 'guido': 0.05; 'true,': 0.05; 'subject:Python': 0.06; 'dev': 0.07; 'string': 0.09; '2.3,': 0.09; '2to3': 0.09; 'deprecated': 0.09; 'obsolete': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'python': 0.11; 'jan': 0.12; 'random': 0.14; 'changes': 0.15; 'alteration.': 0.16; 'backwards': 0.16; 'classes)': 0.16; 'discussion.': 0.16; 'floats;': 0.16; 'numbers;': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'record,': 0.16; 'reedy': 0.16; 'repr()': 0.16; 'strength': 0.16; 'wrote:': 0.18; 'wed,': 0.18; 'module': 0.19; '3.0': 0.19; 'examples': 0.20; 'not,': 0.20; 'written': 0.21; 'proposed': 0.22; 'header:User-Agent:1': 0.23; '2.x': 0.24; 'header:X-Complaints-To:1': 0.27; 'header:In-Reply- To:1': 0.27; 'idea': 0.28; 'specifically': 0.29; 'am,': 0.29; '(like': 0.30; 'code': 0.31; '(although': 0.31; '3.x': 0.31; "d'aprano": 0.31; 'exceptions': 0.31; 'relies': 0.31; 'steven': 0.31; 'run': 0.32; 'another': 0.32; '(e.g.': 0.33; 'style': 0.33; 'but': 0.35; 'there': 0.35; 'version': 0.36; 'sequence': 0.36; 'next': 0.36; 'initially': 0.38; 'to:addr:python-list': 0.38; 'little': 0.38; 'received:71': 0.39; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'users': 0.40; 'negative': 0.60; 'removing': 0.60; 'break': 0.61; 'numbers': 0.61; 'skip:n 10': 0.64; 'more': 0.64; 'great': 0.65; 'removal': 0.74; 'guaranteed': 0.75; 'bastion': 0.84; 'float,': 0.84; 'mind:': 0.84; 'received:fios.verizon.net': 0.84; 'removals': 0.84; 'emerged': 0.91; 'treatment': 0.95 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Terry Reedy Subject: Re: Python 3 is killing Python Date: Thu, 29 May 2014 02:57:57 -0400 References: <5386b19c$0$11109$c3e8da3@news.astraweb.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Gmane-NNTP-Posting-Host: pool-71-175-90-87.phlapa.fios.verizon.net User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 In-Reply-To: <5386b19c$0$11109$c3e8da3@news.astraweb.com> 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: 47 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1401346808 news.xs4all.nl 2884 [2001:888:2000:d::a6]:47343 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:72222 On 5/29/2014 12:03 AM, Steven D'Aprano wrote: > On Wed, 28 May 2014 20:41:53 -0400, Terry Reedy wrote: > >> Claim: Another great strength of Python 2 was that programs written in >> it would almost always run on the next version of Python without much >> alteration. >> >> True. > > True, but only because of the weasel-words "almost always", and "without > much alteration". > > And for the record, for many (although not all) programs written in > Python 2.7, it is still true that they will often run in Python 3 with > little or no modification. > > >> Changes and removals of deprecated features (like old style >> classes) were put off until 3.0 (at the request of some of the noiser >> users). I am specifically thinking of int / int -> float, which Guido initially proposed for 2.5 after warnings in 2.3, 2.4. The idea of 3.0 with more breakage and 2to3 emerged during that discussion. > That's a little unfair. Noisy users or not, Python Dev has always taken > backwards compatibility seriously. > > Nevertheless, there have been some big changes to Python 2.x that > *didn't* wait for 3.x to break backwards compatibility. A few examples > that come to mind: > > - removing string exceptions for good in 2.6; > - changes to the treatment in hex() of negative numbers; > - the repr() of floats; > - changes to the sequence of random numbers generated by the > random number module (e.g. while random.random() is > guaranteed to return the same sequence of values, > random.choice is not); > - removal of obsolete modules like bastion and rotor. > > Any and all of these things can break code that relies on them. -- Terry Jan Reedy