Path: csiph.com!newsfeed.hal-mli.net!feeder3.hal-mli.net!newsfeed.hal-mli.net!feeder1.hal-mli.net!newsfeed.xs4all.nl!newsfeed1.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; 'permitted': 0.07; 'keys,': 0.09; 'slices': 0.09; 'wrapper': 0.09; 'def': 0.12; 'aggregation,': 0.16; 'behave': 0.16; 'copying.': 0.16; 'dict': 0.16; 'from:addr:cs': 0.16; 'from:addr:zip.com.au': 0.16; 'from:name:cameron simpson': 0.16; 'message-id:@cskk.homeip.net': 0.16; 'overridden': 0.16; 'received:211.29': 0.16; 'received:211.29.132': 0.16; 'received:cskk.homeip.net': 0.16; 'received:homeip.net': 0.16; 'received:optusnet.com.au': 0.16; 'received:syd.optusnet.com.au': 0.16; 'redundant': 0.16; 'rhodes': 0.16; 'simpson': 0.16; 'storing': 0.16; 'subclass': 0.16; 'subclassing': 0.16; 'writable': 0.16; 'all.': 0.16; 'wrote:': 0.18; 'header:User-Agent:1': 0.23; 'bytes': 0.24; 'cheers,': 0.24; 'performing': 0.26; 'least': 0.26; 'world,': 0.26; 'header:In- Reply-To:1': 0.27; 'idea': 0.28; 'leave': 0.29; 'have,': 0.30; 'fast.': 0.31; 'class': 0.32; 'skip:_ 10': 0.34; 'subject:from': 0.34; 'but': 0.35; 'there': 0.35; 'received:com.au': 0.36; 'skip:> 10': 0.36; 'doing': 0.36; 'implement': 0.38; 'received:211': 0.38; 'whatever': 0.38; 'to:addr:python-list': 0.38; 'to:addr:python.org': 0.39; 'how': 0.40; 'then,': 0.60; 'simply': 0.61; 'simple': 0.61; 'first': 0.61; 'content-disposition:inline': 0.62; 'subject:get': 0.81; 'idiots': 0.84; 'julie': 0.84; 'thing...': 0.84 Date: Tue, 4 Mar 2014 09:02:07 +1100 From: Cameron Simpson To: python-list@python.org Subject: Re: how to get bytes from bytearray without copying MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) References: X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.1 cv=Wu4Sb7vv c=1 sm=1 tr=0 a=YuQlxtEQCowy2cfE5kc7TA==:117 a=YuQlxtEQCowy2cfE5kc7TA==:17 a=ZtCCktOnAAAA:8 a=PO7r1zJSAAAA:8 a=LcaDllckn3IA:10 a=GCYxRCg_PokA:10 a=IkcTkHD0fZMA:10 a=vrnE16BAAAAA:8 a=pGLkceISAAAA:8 a=LvLpXEYgAAAA:8 a=gsBrBudCXCulw6qD__4A:9 a=QEXdDO2ut3YA:10 a=MSl-tDqOz04A:10 a=WjE-N-J3fjQA:10 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: 32 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1393884137 news.xs4all.nl 2916 [2001:888:2000:d::a6]:39689 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:67592 On 03Mar2014 09:15, Juraj Ivančić wrote: > On 3.3.2014. 1:44, Cameron Simpson wrote: > >>ValueError: cannot hash writable memoryview object > > > >Have you considered subclassing memoryview and giving the subclass > >a __hash__ method? > > I have, and then, when I failed to subclass it, I considered doing > aggregation, and make it behave byte-like. But how to implement the > overridden __hash__ method? It will still require at least *some* > redundant copying. And there is the slicing thing... the whole idea > started to feel like I was performing tonsillectomy through the anal > cavity. Write a wrapper class instead and use: def __hash__(self): return id(self) Simple and fast. Unless you need slices with the same content to hash the same (eg storing them as dict keys, or in sets). And alternative would be a simple hash of the first few bytes in whatever slice you had. Cheers, -- Cameron Simpson Why is it so hard for people to simply leave people alone? But, the answer comes to me: they are idiots and in a perfect world, I would be permitted to kill them all. - Julie Rhodes