Path: csiph.com!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder2.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; 'python,': 0.01; 'example:': 0.03; 'distinct': 0.04; 'subject:Python': 0.05; 'python': 0.08; 'arguments,': 0.09; 'instance.': 0.09; 'invokes': 0.09; 'def': 0.13; 'model,': 0.15; '(besides': 0.16; '*class': 0.16; '__init__': 0.16; 'confusing.': 0.16; 'simplest': 0.16; 'subject:classes': 0.16; 'cc:addr:python-list': 0.16; 'syntax': 0.16; 'wrote:': 0.18; 'exists': 0.18; 'instance': 0.18; 'seems': 0.20; 'cc:no real name:2**0': 0.21; 'header:In-Reply-To:1': 0.22; '"it\'s': 0.23; 'translated': 0.23; 'way?': 0.23; 'defined': 0.24; 'cc:2**0': 0.26; 'classes': 0.26; 'function': 0.27; 'not.': 0.28; 'explicit': 0.29; 'class': 0.29; 'example': 0.29; 'problem': 0.29; 'skip:b 20': 0.29; 'cc:addr:python.org': 0.29; 'subject:?': 0.31; 'familiar': 0.32; 'idea': 0.32; "isn't": 0.33; 'there': 0.33; "won't": 0.33; 'header:User-Agent:1': 0.33; 'steven': 0.34; 'done': 0.34; 'jump': 0.34; 'something': 0.35; 'with.': 0.37; 'but': 0.37; 'skip:" 10': 0.37; 'using': 0.37; 'skip:_ 10': 0.38; 'uses': 0.38; 'data': 0.38; 'initially': 0.39; 'cannot': 0.39; 'called': 0.40; 'missing': 0.40; "you'll": 0.61; 'conclusions': 0.84 X-IronPort-AV: E=Sophos;i="4.73,637,1325458800"; d="scan'208";a="269724" X-Virus-Scanned: amavisd-new at zimbra.sequans.com Date: Fri, 23 Mar 2012 15:19:55 +0100 From: Jean-Michel Pichavant User-Agent: Mozilla-Thunderbird 2.0.0.24 (X11/20100328) MIME-Version: 1.0 To: Steven Lehar Subject: Re: Python classes: Simplify? References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit 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: 51 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1332512488 news.xs4all.nl 6934 [2001:888:2000:d::a6]:47727 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:22073 Steven Lehar wrote: > It seems to me that the Python class system is needlessly confusing. > Am I missing something? > > For example in the class Complex given in the documentation > > *class Complex:* > * def __init__(self, realpart, imagpart):* > * self.r = realpart* > * self.i = imagpart* > * > * > *x = Complex(3.0, -4.5)* > > I initially found it profoundly confusing that __init__( ) calls for 3 > arguments, but you call Complex( ) with 2. Furthermore, why not call > the initialization function after the class name as is done in other > languages? Isn't that the simplest conceptually? Demonstrating with > the above example: > In python, writting obj.method() will be translated into method(obj) so any instance method has a #arg + 1 arguments, something you'll get familiar with. Furthermore, Complex(3.0, -4.5) invokes 2 functions : __new__ and __init__. __new__ is the "constructor", this is the function that returns an instance. __init__ is an initializer, at the time it's called the instance already exists and is viable. > *class Complex:* > * def Complex(realpart, imagpart):* > * Complex.r = realpart* > * Complex.i = imagpart* > * > * > *x = Complex(3.0, -4.5)* > * > * > Is there a good reason why classes cannot be defined that way? > (Besides the problem of backward-compatibility) > Python uses a different data model, it is a very good idea to mark theses differences using an explicit distinct syntax so that people won't jump into false conclusions like "it's like C or Java". It is not. JM JM