Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail From: Michael Selik Newsgroups: comp.lang.python Subject: Re: UserList - which methods needs to be overriden? Date: Fri, 10 Jun 2016 13:18:56 +0000 Lines: 42 Message-ID: References: <1f4d1918-1e38-abba-aca7-830d91d35bd4@shopzeus.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Trace: news.uni-berlin.de f5d50ZkcGPvNOY7PYENfbghk7Kb14cy9xFU2Mrx1QRDA== 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; 'preferably': 0.05; 'that?': 0.05; 'implements': 0.07; 'override': 0.07; 'collections': 0.09; 'loop.': 0.09; 'methods,': 0.09; 'subclass': 0.09; 'subject:which': 0.09; ':-)': 0.12; 'thu,': 0.15; '2016': 0.16; 'overriding': 0.16; 'pop()': 0.16; 'received:io': 0.16; 'received:psf.io': 0.16; 'wrote:': 0.16; 'to:name:python- list@python.org': 0.20; 'to:2**1': 0.21; '(the': 0.22; 'wrote': 0.23; 'header:In-Reply-To:1': 0.24; 'fri,': 0.27; 'message- id:@mail.gmail.com': 0.27; 'object,': 0.27; 'fast.': 0.29; "i'm": 0.30; 'extend': 0.31; 'functional': 0.32; 'point': 0.33; 'michael': 0.33; "i'll": 0.33; 'list': 0.34; 'received:google.com': 0.35; 'skip:c 30': 0.35; 'quite': 0.35; 'but': 0.36; 'should': 0.36; 'there': 0.36; 'received:209.85': 0.36; 'to:addr:python-list': 0.36; 'subject:?': 0.36; 'subject:: ': 0.37; 'method': 0.37; 'received:209': 0.38; 'why': 0.39; 'sure': 0.39; 'to:addr:python.org': 0.40; 'your': 0.60; 'more': 0.63; 'beautiful': 0.66; 'sans': 0.72; 'discover': 0.73; 'nagy': 0.84; 'vera': 0.84; 'abc': 0.91; 'subject:needs': 0.93 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=PdBDMUlRX2bCF12NX/QsmP9cbdHCPWM/qTxR8zJbohI=; b=BGeZa8kpn943pTyZuYod8WRG+sV6UeaBe6zbNtMYFCrgF1NlGsKXAfwzwcOpNXHwz0 yT4Lb/vNI+laWRv7uDnJR3PntZddUWse8nsFJHj7qd7Rj6Tk/0jrDDg7qBrJZFIOhnDL jEnG3+TUHnaXDKGEVqGLVS0gP0q0aI47Q/GL2RLNFDNQ0FNq83RjvuNEtp6NnTA1d7sX hvAxOVmgn11M70BypnSbJkD1Uo0o58WEceH/yhz8H9d84gQvyEmmeKV0VL6tESLOn/9D ULBIPOGwmGuD2YtD73XWyjuWqmu0TTBBg7wwbJmFrtvLbjuaeXW0yk/oeaT89J5l2CrZ qFYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to; bh=PdBDMUlRX2bCF12NX/QsmP9cbdHCPWM/qTxR8zJbohI=; b=Zg8Ke9tdjhanf6gfWC7Ip43JFny6zicGD2181p4vjUm5S1k9F8urv/bg2nXDBKKPty cggmDlBrTHGVMFcE3WNvrFiSWkWCBA0p/7pMdFkWfTlL+sMVLWbS1hGSinrDkFSY94br r7HerSpOMR9Qx1nRJvH1Md4M3vdJhkpKMy5I0cPpPNMjgVE2W15s7V+6WtJgmYxZPiGf q0GNGhC2e/uUFPYZrFsdQpukAOclHrnU7FQpAw0kp8Nd3gEy01i4G1RcmlnqGcXt6lCR H8fyLRzQLRHXuRKf2cliF0GvRrP68BIs3+OuNAP26wr+D+UzaxNkuxkcrB9Z79U7W6fv aWgw== X-Gm-Message-State: ALyK8tLFxJrx300am/PXMmYbHwy61cwfnVqia+HtzkLVoKkpYSU/AGZVo3oZt6W6Udu6K+mUh2kwFH36XEcjXQ== X-Received: by 10.141.2.132 with SMTP id e126mr1816634qhd.55.1465564746487; Fri, 10 Jun 2016 06:19:06 -0700 (PDT) In-Reply-To: <1f4d1918-1e38-abba-aca7-830d91d35bd4@shopzeus.com> X-Content-Filtered-By: Mailman/MimeDel 2.1.22 X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Mailman-Original-Message-ID: X-Mailman-Original-References: <1f4d1918-1e38-abba-aca7-830d91d35bd4@shopzeus.com> Xref: csiph.com comp.lang.python:109785 On Fri, Jun 10, 2016, 4:05 AM Nagy L=C3=A1szl=C3=B3 Zsolt wrote: > 2016.06.10. 0:38 keltez=C3=A9ssel, Michael Selik =C3=ADrta: > > On Thu, Jun 9, 2016 at 5:07 AM Nagy L=C3=A1szl=C3=B3 Zsolt > wrote: > >> I would like to create a collections.UserList subclass that can notify >> others when the list is mutated. >> > > Why not subclass MutableSequence instead? The ABC will tell you which > methods to override (the abstract ones). The mixin methods rely on those > overrides. > > I'm not sure wich one is the best. Peter wrote that UserList was left in > collections only for backward compatiblity. This might be a point against > using UserList. The thing with MutableSequence is that it is quite > inefficient. For example, it implements clear() by calling pop() in a loo= p. > It implements extend() by calling append() in a loop. And we all know tha= t > the built-in extend() method of the list object is much more efficient. I= t > is true that by overriding the abstract methods, I'll get a functional li= st > like object, but we all know that > > There should be one-- and preferably only one --obvious way to do it. > > > Which one is that? :-) > The easiest, most beautiful way that is sufficiently fast. Use MutableSequence until you discover that extend is actually the bottleneck in your program. >