Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.xs4all.nl!newsfeed2.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; 'from:addr:yahoo.co.uk': 0.04; 'lawrence': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'subject:method': 0.09; 'python': 0.11; 'def': 0.12; 'language.': 0.14; 'a(object):': 0.16; 'hierarchy': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'subject:class': 0.16; 'language': 0.16; 'wrote:': 0.18; 'trying': 0.19; 'implementing': 0.19; 'header:User-Agent:1': 0.23; 'header:X-Complaints-To:1': 0.27; 'header:In-Reply-To:1': 0.27; 'besides': 0.30; "i'm": 0.30; 'too.': 0.31; '3.x': 0.31; 'class': 0.32; 'skip:_ 10': 0.34; "i'd": 0.34; 'subject:from': 0.34; 'but': 0.35; 'there': 0.35; 'curious': 0.36; 'i.e.': 0.36; 'jason': 0.38; 'to:addr:python-list': 0.38; 'rather': 0.38; 'explain': 0.39; 'sure': 0.39; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'how': 0.40; "you're": 0.61; 'our': 0.64; 'charset:windows-1252': 0.65 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Mark Lawrence Subject: Re: Calling a derived class's constructor from a parent method Date: Wed, 14 Jan 2015 17:05:27 +0000 References: Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Gmane-NNTP-Posting-Host: host-92-24-222-48.ppp.as43234.net User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 In-Reply-To: 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: 33 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1421255143 news.xs4all.nl 2916 [2001:888:2000:d::a6]:33338 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:83767 On 14/01/2015 16:45, jason wrote: > If I have a class hierarchy like so: > > > class A(object): > def __init__(self, s): > self.s = s > def foo(self, s): > return A(s) > > class B(A): > def __init__(self, s): > A.__init__(self, s) > > If I make a B: > > b = B(0) > > I'd like b.foo(1) to return an instance of B. Is there a way to do that besides implementing a construct(self, s) for each part of the hierarchy? I.e. is there a way for the base class to look at self and find out what type to create? > > I'm using Python 2.7.5, but I'm curious what the 3.x answer is too. > I'm confused, can you please explain what you're trying to achieve rather than how you're trying to achieve it and I'm sure that others will give better answers than I can :) -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence