Path: csiph.com!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder1.enfer-du-nord.net!feeds.phibee-telecom.net!newsfeed.xs4all.nl!newsfeed5.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 0.000 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'example:': 0.03; 'raised': 0.07; 'try:': 0.07; 'errors,': 0.09; 'oh,': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'terry': 0.09; 'tuple': 0.09; 'cases': 0.15; 'both.': 0.16; 'enough.': 0.16; 'indexerror:': 0.16; 'keyerror': 0.16; 'mapping,': 0.16; 'message- id:@dough.gmane.org': 0.16; 'pair,': 0.16; 'popping': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'reedy': 0.16; 'true:': 0.16; 'wrote:': 0.17; 'mechanism': 0.17; 'jan': 0.18; '31,': 0.22; 'example': 0.23; 'pass': 0.25; 'header :In-Reply-To:1': 0.25; 'header:User-Agent:1': 0.26; 'possibly': 0.27; 'replace': 0.27; 'header:X-Complaints-To:1': 0.28; 'chris': 0.28; 'class': 0.29; 'usually': 0.30; 'code': 0.31; 'url:python': 0.32; 'to:addr:python-list': 0.33; 'another': 0.33; 'done': 0.34; 'list': 0.35; 'sequence': 0.35; 'pm,': 0.35; 'continue': 0.35; 'there': 0.35; 'received:org': 0.36; 'except': 0.36; 'but': 0.36; 'url:org': 0.36; 'url:library': 0.36; 'subject:: ': 0.38; 'url:docs': 0.38; 'to:addr:python.org': 0.39; 'easily': 0.39; 'header:Received:5': 0.40; 'is.': 0.62; 'decided': 0.65; 'book.': 0.65; 'jul': 0.65; 'subject:skip:A 10': 0.75; 'received:fios.verizon.net': 0.84 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Terry Reedy Subject: Re: NameError vs AttributeError Date: Tue, 31 Jul 2012 20:14:01 -0400 References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; 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:13.0) Gecko/20120614 Thunderbird/13.0.1 In-Reply-To: X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.12 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: 1343780060 news.xs4all.nl 6857 [2001:888:2000:d::a6]:45179 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:26332 On 7/31/2012 4:49 PM, Chris Kaynor wrote: > On Tue, Jul 31, 2012 at 1:21 PM, Terry Reedy > wrote: > > Another example: KeyError and IndexError are both subscript errors, > but there is no SubscriptError superclass, even though both work > thru the same mechanism -- __getitem__. The reason is that there is > no need for one. In 'x[y]', x is usually intented to be either a > sequence or mapping, but not possibly both. In the rare cases when > one wants to catch both errors, one can easily enough. To continue > the example above, popping an empty list and empty set produce > IndexError and KeyError respectively: > > try: > while True: > process(pop()) > except (KeyError, IndexError): > pass # empty collection means we are done > > There is a base type for KeyError and IndexError: LookupError. > > http://docs.python.org/library/exceptions.html#exception-hierarchy Oh, so there is. Added in 1.5 strictly as a never-directly-raised base class for the above pair, now also directly raised in codecs.lookup. I have not decided if I want to replace the tuple in the code in my book. -- Terry Jan Reedy