Path: csiph.com!usenet.pasdenom.info!aioe.org!news.stack.nl!newsfeed.xs4all.nl!newsfeed6.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; 'interpreter': 0.04; 'memory.': 0.05; 'none,': 0.05; 'sized': 0.07; 'python': 0.09; '32-bit': 0.09; 'nameerror:': 0.09; 'porting': 0.09; 'subclass': 0.09; 'subject:()': 0.09; 'unexpected': 0.09; '"hello': 0.16; 'cool.': 0.16; 'crashes': 0.16; 'mistake.': 0.16; 'oct': 0.16; 'subject:array': 0.16; 'wrote:': 0.17; 'element': 0.17; 'integer': 0.17; 'processor': 0.17; 'appears': 0.18; 'variable': 0.20; 'java': 0.21; '"",': 0.22; 'noted': 0.22; 'of.': 0.22; 'defined': 0.22; 'example': 0.23; 'programming': 0.23; 'nearly': 0.23; 'header:In-Reply-To:1': 0.25; 'looks': 0.26; '(most': 0.27; 'am,': 0.27; 'embedded': 0.27; 'possibly': 0.27; 'realize': 0.27; 'message-id:@mail.gmail.com': 0.27; "doesn't": 0.28; 'run': 0.28; 'omitted': 0.29; 'overhead': 0.29; 'steven': 0.29; 'case,': 0.29; 'definition': 0.29; 'probably': 0.29; 'class': 0.29; 'that.': 0.30; 'filled': 0.30; 'notes': 0.30; 'received:209.85.215.46': 0.30; 'error': 0.30; 'lists': 0.31; 'system,': 0.32; 'file': 0.32; 'running': 0.32; 'anywhere': 0.33; 'explains': 0.33; 'ram': 0.33; 'traceback': 0.33; 'to:addr:python-list': 0.33; 'likely': 0.33; "can't": 0.34; 'received:google.com': 0.34; 'list': 0.35; 'lists.': 0.35; "won't": 0.35; 'received:209.85': 0.35; 'next': 0.35; 'list.': 0.35; 'wanted': 0.36; 'alone': 0.36; 'method': 0.36; 'should': 0.36; 'itself': 0.37; 'being': 0.37; 'why': 0.37; 'virtual': 0.37; 'received:209': 0.37; 'subject:: ': 0.38; 'some': 0.38; 'system.': 0.39; 'to:addr:python.org': 0.39; 'space': 0.39; 'where': 0.40; 'header:Received:5': 0.40; 'your': 0.60; 'capable': 0.63; 'more': 0.63; 'due': 0.66; 'online': 0.70; 'million': 0.72; 'power': 0.74; 'low': 0.83; 'to:name:python': 0.84; 'behaviors.': 0.91 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type:content-transfer-encoding; bh=xjrjQIqTOQgxdYQOi5l0DW9bQcMB6x/G6kua3R5sRe8=; b=u0GWVZutZCQx5FjxcSYjWxTuo5W5M3WqYDtQoQ2mmGAM/DfG9fF9fUpPcBJ3BiXGEq KGmwa6LTHEocPa9piJ37cqZwPvlJeya3bH2g46wBeUeYc+1GrnSkUxpzlkychOAVSIBJ CiVII7U36Cobxk8OakmxQPDVS9rcONydFRkXV1Chsreemjab5/YwbAOXVQuxLU+g0TG4 VgOkONPJTO4vISGC3/Z0XShx2VAullD7wSYi+9qAfCck3A0djfCR7oGP3ribJR2pM9Yj 5wfs586z+6NT+P7h8FTNeSEFx9RNRYER1cPbjpf+/k5m94KC9TrZkzbB+Y2V8Izf5Qem XdxA== MIME-Version: 1.0 In-Reply-To: <508E1BC9.3000308@r3dsolutions.com> References: <6998a955-7b34-4f4f-b8d6-62d1028f7561@googlegroups.com> <4c024364-84df-403b-8b9e-4a4c8f06121c@googlegroups.com> <508e6649$0$29967$c3e8da3$5496439d@news.astraweb.com> <508E1BC9.3000308@r3dsolutions.com> From: Ian Kelly Date: Mon, 29 Oct 2012 11:09:01 -0600 Subject: Re: Negative array indicies and slice() To: Python Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable 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: 48 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1351530574 news.xs4all.nl 6865 [2001:888:2000:d::a6]:57276 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:32405 On Oct 29, 2012 7:10 AM, "Andrew Robinson" wrote= : > I will be porting Python 3.xx to a super low power embedded processor (MS= P430), both space and speed are at a premium. > Running Python on top of Java would be a *SERIOUS* mistake. .NET won't e= ven run on this system. etc. If that's the case, then running Python at all is probably a mistake. You know the interpreter alone has an overhead of nearly 6 MB? > Yes, I realize that. > But, why can't I just overload the existing __getitem__ for lists and not= bother writing an entire class? You can just overload that one method in a subclass of list. Being able to monkey-patch __getitem__ for the list class itself would not be advisable, as it would affect all list slicing anywhere in your program and possibly lead to some unexpected behaviors. > Hmmm.. > Let's try your example exactly as shown... > > "hello world"[aslice] > > Traceback (most recent call last): > File "", line 1, in > NameError: name 'aslice' is not defined > > WOW. Cool. > Where did the blanks *actually* get filled in? Or HOW WILL they in your = next post? It appears that Steven omitted the definition of aslice by mistake. It looks like it should have been: aslice =3D slice(4, None, 2) > Looking at some of the online programming notes -- a slice apparently do= esn't use an integer storage variable that is capable of arbitrary expansio= n. =3D-O -- and hence, won't work for very large sized lists. That actuall= y explains some crashes I have noted in the past when working with 20 milli= on element lists that I wanted a slice of. I had *plenty* of ram on that s= ystem. 20 million is nothing. On a 32-bit system, sys.maxsize =3D=3D 2 ** 31 - 1. If the error you were seeing was MemoryError, then more likely you were running into dynamic allocation issues due to fragmentation of virtual memory.