Path: csiph.com!usenet.pasdenom.info!news.albasani.net!newsfeed.freenet.ag!news2.euro.net!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; 'permitted': 0.07; 'builtin': 0.09; 'classes.': 0.09; 'feature,': 0.09; 'patch.': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'restriction': 0.09; 'python': 0.11; 'jan': 0.12; '"in': 0.16; 'bool': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'reedy': 0.16; 'singleton': 0.16; 'subclass': 0.16; 'subject: \n ': 0.16; 'subject:OOP': 0.16; 'subject:object': 0.16; 'subject:possible': 0.16; 'subject:programming': 0.16; 'subject:type': 0.16; 'exception': 0.16; 'language': 0.16; 'wrote:': 0.18; 'header:User-Agent:1': 0.23; 'case.': 0.24; 'documented': 0.24; 'mon,': 0.24; 'class.': 0.26; 'subject:/': 0.26; 'header:X-Complaints-To:1': 0.27; 'header:In-Reply-To:1': 0.27; 'leave': 0.29; "d'aprano": 0.31; 'steven': 0.31; 'classes': 0.35; 'case,': 0.35; 'more,': 0.35; 'one,': 0.35; 'there': 0.35; 'possible': 0.36; 'two': 0.37; 'to:addr:python-list': 0.38; 'issue': 0.38; 'pm,': 0.38; 'does': 0.39; 'itself': 0.39; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'received:173': 0.61; 'first': 0.61; 'skip:n 10': 0.64; 'decided': 0.64; 'subject:The': 0.64; 'here': 0.66; 'believe': 0.68; 'other.': 0.75; '10:32': 0.84; 'received:fios.verizon.net': 0.84; '2013': 0.98 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Terry Jan Reedy Subject: Re: The type/object distinction and possible synthesis of OOP and imperative programming languages Date: Mon, 15 Apr 2013 23:17:36 -0400 References: <516bd241$0$29872$c3e8da3$5496439d@news.astraweb.com> <516C3C44.6010706@rece.vub.ac.be> <516cb85b$0$29977$c3e8da3$5496439d@news.astraweb.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Gmane-NNTP-Posting-Host: pool-173-75-251-66.phlapa.fios.verizon.net User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 In-Reply-To: <516cb85b$0$29977$c3e8da3$5496439d@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: 29 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1366082270 news.xs4all.nl 2662 [2001:888:2000:d::a6]:37612 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:43658 On 4/15/2013 10:32 PM, Steven D'Aprano wrote: > On Mon, 15 Apr 2013 20:52:58 -0400, Terry Jan Reedy wrote: >> Some builtin classes cannot be subclassed. There is an issue to document >> which better. That does not mean that it is not a class. > > > I think it is also important to document whether that is a language > feature, or a mere restriction of the implementation. There is an > important distinction to be made between: > > "In CPython, you cannot subclass slice or FunctionType. Other Pythons may > have more, or fewer, restrictions." > > and: > > "No language that calls itself Python is permitted to allow slice and > FunctionType to be subclassable." > > > If I had a say in this, I would vote for the first case, with the > possible exception of documented singleton types like NoneType and bool. I will keep the above in mind if I write or review a patch. here are 4 non-subclassable builtin classes. Two are already documented. Bool in one, forget which other. I believe it was recently decided to leave the other two as is given the absence of any practical use case.