Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!ecngs!feeder2.ecngs.de!newsfeed.freenet.ag!news2.euro.net!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 0.004 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'attribute': 0.05; 'diff': 0.05; 'modified': 0.05; 'modify': 0.05; '(it': 0.09; 'subclass': 0.09; 'to:addr:comp.lang.python': 0.09; 'cc:addr:python-list': 0.10; "wouldn't": 0.11; 'properties,': 0.16; 'subject:object': 0.16; 'subject:when': 0.16; 'using,': 0.16; 'utc,': 0.16; 'wrote:': 0.17; 'certainly': 0.17; 'trying': 0.21; 'explicit': 0.22; 'wednesday,': 0.22; "i'd": 0.22; 'cc:2**0': 0.23; 'properties': 0.24; 'cc:no real name:2**0': 0.24; 'cc:addr:python.org': 0.25; 'header:In-Reply-To:1': 0.25; 'header :User-Agent:1': 0.26; 'guess': 0.27; 'chris': 0.28; 'comparison': 0.29; 'gather': 0.29; 'types.': 0.29; 'objects': 0.29; 'probably': 0.29; 'that.': 0.30; 'function': 0.30; 'could': 0.32; 'operations': 0.33; 'changed': 0.34; 'received:google.com': 0.34; 'ben': 0.35; 'too.': 0.35; 'received:209.85': 0.35; 'something': 0.35; 'but': 0.36; 'expensive': 0.36; 'rather': 0.37; 'received:209': 0.37; 'subject:: ': 0.38; 'mark': 0.38; 'perform': 0.38; 'store': 0.38; 'object': 0.38; 'skip:l 20': 0.38; 'several': 0.39; 'performance': 0.39; 'end': 0.40; 'burden': 0.65; 'differences': 0.65; 'goal': 0.74; '2013': 0.84; 'effectively,': 0.84; 'having,': 0.84; 'snapshot': 0.84; 'snapshots': 0.84; 'subject:its': 0.84 X-Received: by 10.49.29.99 with SMTP id j3mr630504qeh.38.1362588969946; Wed, 06 Mar 2013 08:56:09 -0800 (PST) Newsgroups: comp.lang.python Date: Wed, 6 Mar 2013 08:56:09 -0800 (PST) In-Reply-To: Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=82.5.8.209; posting-account=uOuzAgkAAACK55ip5nYJi22tcCxQUWqT References: User-Agent: G2/1.0 X-Google-Web-Client: true X-Google-IP: 82.5.8.209 MIME-Version: 1.0 Subject: Re: Creating an object that can track when its attributes are modified From: Ben Sizer To: comp.lang.python@googlegroups.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: python-list@python.org 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: , Message-ID: Lines: 26 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1362588979 news.xs4all.nl 6854 [2001:888:2000:d::a6]:54331 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:40647 On Wednesday, 6 March 2013 16:22:56 UTC, Chris Angelico wrote: >=20 > Effectively, you would need to have a > subclass of list/dict/tuple/whatever that can respond to the change.=20 This is certainly something I'd be interested in having, but I guess that w= ould be fragile since the user would have the burden of having to remember = to use those types. > What's the goal of this class? Can you achieve the same thing by > using, perhaps, a before-and-after snapshot of a JSON-encoded form of > the object? >=20 I need to be able to perform complex operations on the object that may modi= fy several properties, and then gather the properties at the end as an effi= cient way to see what has changed and to store those changes. Any compariso= n of before-and-after snapshots could work in theory, but in practice it co= uld be expensive to produce the snapshots on larger objects and probably ex= pensive to calculate the differences that way too. Performance is important= so I would probably just go for an explicit function call to mark an attri= bute as having been modified rather than trying to do a diff like that. (It= wouldn't work for rollbacks, but I can accept that.) --=20 Ben Sizer