Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!selfless.tophat.at!newsfeed.xs4all.nl!newsfeed6.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; '>>>>': 0.09; 'from:addr:ethan': 0.09; 'from:addr:stoneleaf.us': 0.09; 'from:name:ethan furman': 0.09; 'hash': 0.09; 'message- id:@stoneleaf.us': 0.09; 'received:gator410.hostgator.com': 0.09; 'url:dev': 0.09; '~ethan~': 0.09; 'this:': 0.10; 'def': 0.12; 'wrote:': 0.14; 'differently:': 0.16; 'equal,': 0.16; 'furman': 0.16; 'python3:': 0.16; 'received:72.11': 0.16; 'received:72.11.125': 0.16; 'received:72.11.125.166': 0.16; 'cc:addr:python-list': 0.17; 'header:In-Reply-To:1': 0.21; 'cc:2**0': 0.22; 'cc:no real name:2**0': 0.23; 'trying': 0.23; 'objects': 0.23; 'somebody': 0.25; 'compare': 0.26; 'example': 0.27; "i'm": 0.27; 'class': 0.29; 'cc:addr:python.org': 0.30; 'equal': 0.31; "isn't": 0.33; '...': 0.34; 'thinking': 0.34; 'header:User-Agent:1': 0.35; 'several': 0.36; 'url:docs': 0.37; 'two': 0.37; 'url:python': 0.38; 'hoping': 0.38; 'url:org': 0.38; 'but': 0.38; 'docs': 0.38; 'subject:: ': 0.38; 'said': 0.39; 'happen': 0.60; 'received:websitewelcome.com': 0.67; 'received:69.93': 0.67; '13)': 0.84 Date: Fri, 20 May 2011 10:57:42 -0700 From: Ethan Furman User-Agent: Thunderbird 1.5.0.10 (Windows/20070221) MIME-Version: 1.0 To: Peter Otten <__peter__@web.de> Subject: Re: hash values and equality References: <4DD2C2A5.3080403@stoneleaf.us> <4DD2D89D.4000303@stoneleaf.us> <4DD2F661.2050005@stoneleaf.us> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator410.hostgator.com X-AntiAbuse: Original Domain - python.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - stoneleaf.us X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: mail.admailinc.com ([192.168.10.136]) [72.11.125.166]:1706 Cc: python-list@python.org 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: 42 NNTP-Posting-Host: 82.94.164.166 X-Trace: 1305913522 news.xs4all.nl 49038 [::ffff:82.94.164.166]:38039 X-Complaints-To: abuse@xs4all.nl Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:5863 Peter Otten wrote: > Ethan Furman wrote: > >> Several folk have said that objects that compare equal must hash equal, >> and the docs also state this >> http://docs.python.org/dev/reference/datamodel.html#object.__hash__ >> >> I'm hoping somebody can tell me what horrible thing will happen if this >> isn't the case? Here's a toy example of a class I'm thinking of writing >> that will compare equal with int's, but hash differently: >> >> --> class Wierd(): >> ... def __init__(self, value): >> ... self.value = value >> ... def __eq__(self, other): >> ... return self.value == other >> ... def __hash__(self): >> ... return hash((self.value + 13) ** 3) >> ... > > Try this: > >>>> d = {Wierd(1): 0} >>>> 1 in d > False >>>> 1 in d.keys() > True > My apologies -- I'm trying this in Python3: --> two in d True --> two in d.keys() True --> --> 2 in d True --> 2 in d.keys() True ~Ethan~