Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!feeds.phibee-telecom.net!newsfeed.xs4all.nl!newsfeed1a.news.xs4all.nl!xs4all!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; 'subject:error': 0.03; 'interpreter': 0.05; 'attribute': 0.07; 'compiler': 0.07; 'indices': 0.07; 'variables': 0.07; 'sub': 0.09; 'python': 0.11; 'jan': 0.12; 'stored': 0.12; '24,': 0.16; 'code?': 0.16; 'dict': 0.16; 'globals': 0.16; 'imports': 0.16; "module's": 0.16; 'says...': 0.16; 'sat,': 0.16; 'wrote:': 0.18; 'looked': 0.18; 'variable': 0.18; 'module': 0.19; 'stack': 0.19; '>>>': 0.22; 'memory': 0.22; 'import': 0.22; 'error': 0.23; 'module,': 0.24; 'pointer': 0.24; 'looks': 0.24; 'second': 0.26; 'header:In-Reply- To:1': 0.27; 'correct': 0.29; 'array': 0.29; "doesn't": 0.30; 'statement': 0.30; 'message-id:@mail.gmail.com': 0.30; "i'm": 0.30; 'code': 0.31; 'url:wiki': 0.31; 'location,': 0.31; 'object.': 0.31; 'question:': 0.31; 'url:wikipedia': 0.31; 'handled': 0.32; 'addresses': 0.33; 'could': 0.34; 'message.': 0.35; 'display': 0.35; 'no,': 0.35; 'objects': 0.35; 'but': 0.35; 'received:google.com': 0.35; 'thanks': 0.36; 'url:org': 0.36; 'level': 0.37; 'to:addr:python-list': 0.38; 'pm,': 0.38; 'does': 0.39; 'sure': 0.39; 'to:addr:python.org': 0.39; 'either': 0.39; 'how': 0.40; 'skip:u 10': 0.60; "you're": 0.61; 'first': 0.61; 'name': 0.63; 'map': 0.64; 'article': 0.77; "'foo'": 0.84; '2015': 0.84; 'dict,': 0.84; 'dict.': 0.84 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; bh=7pu+XGrSWo/z6pxHsYzJqwEX3PXWZZA5YjnQLZmkMAQ=; b=jL/IUV3x0PC+bn4eFozw45VNQc7BbxaoQXb1hqW0qlc/6k06CB81mzZEKMyquo/kJp KA3qW2b9+OaxpLDIL/skDufFD8k+0Inx8RO/RIRxJiKmgR8LlKyht9jIAbkpoJODPqZN UN9WFLg0p7INajuCjHE4pUkY9hfxz0qv+Z5D3smkvG0wVgd6IFWDyzZ5tpWGU+rScJ7j 7LW/iM/yQ4mJH3mDSGsdWYz7myAq+lHCfxEuMfEvAJpXegOjZBVIsUPsieCbD1uzolZD yq4Lwa/Sp+Z4rLwq0grcxbegzHscQSwFL70Uqh+sT6jhysSfVU6z8fDnKlYp3XBEqXLo 8rKQ== X-Received: by 10.66.157.5 with SMTP id wi5mr22052776pab.37.1422135972493; Sat, 24 Jan 2015 13:46:12 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <1a194e0a0b738d205de54180fa7@nntp.aioe.org> <54c39366$0$13006$c3e8da3$5496439d@news.astraweb.com> From: Ian Kelly Date: Sat, 24 Jan 2015 14:45:32 -0700 Subject: Re: __bases__ misleading error message To: Python Content-Type: text/plain; charset=UTF-8 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: 46 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1422135976 news.xs4all.nl 2863 [2001:888:2000:d::a6]:52437 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:84496 On Sat, Jan 24, 2015 at 2:14 PM, Mario Figueiredo wrote: > In article <54c39366$0$13006$c3e8da3$5496439d@news.astraweb.com>, > steve+comp.lang.python@pearwood.info says... >> > AttributeError: 'Sub' instance has no attribute '__bases__', >> > AttributeError: 'foo' object has no attribute '__bases__' >> >> The first would be nice. The second is impossible: objects may have no name, >> one name, or many names, and they do not know what names they are bound to. >> So the Sub instance bound to the name 'foo' doesn't know that its name >> is 'foo', so it cannot display it in the error message. > > Thanks for the information! :) > > But that begs the OT question: No, it doesnt. http://en.wikipedia.org/wiki/Begging_the_question > How does Python maps names to memory > addresses in the interpreter? Global variables are looked up in the current stack frame's globals dict. >>> a = 1 >>> b = 2 >>> globals()['a'] 1 >>> globals()['b'] 2 Local variables of functions could be handled the same way, but for efficiency the compiler instead maps the names to indices of a local variable array associated with the stack frame. Either way, at the C level the value stored in the dict or array is a pointer to the memory location of the object. > "__main__" > from module import a_name > y = a_name + 1 > > How does python interpreter know how to map 'name' to the correct memory > location, if this __main__ code is only ran after 'module' code? I'm not sure I'm understanding what you're asking, but the import statement imports the module, looks up "a_name" in that module's globals dict, and binds the same object to a_name in the current module's globals dict.