Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!rt.uk.eu.org!newsfeed.xs4all.nl!newsfeed3.news.xs4all.nl!xs4all!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 0.001 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'subject:not': 0.03; 'attribute': 0.07; 'dynamically': 0.07; 'attributes': 0.09; 'subject:Why': 0.09; 'cc:addr:python-list': 0.11; '-tkc': 0.16; 'descriptors.': 0.16; 'effect.': 0.16; 'from:addr:python.list': 0.16; 'from:addr:tim.thechases.com': 0.16; 'from:name:tim chase': 0.16; 'identifiers': 0.16; 'key/value': 0.16; 'piotr': 0.16; 'subject: \n ': 0.16; 'subject:accessing': 0.16; 'variable.': 0.16; 'way;': 0.16; 'prevent': 0.16; 'wrote:': 0.18; 'pfxlen:0': 0.19; 'later': 0.20; 'meant': 0.20; 'saying': 0.22; 'tests': 0.22; 'cc:addr:python.org': 0.22; "aren't": 0.24; 'driven': 0.24; 'cc:2**0': 0.24; 'cc:no real name:2**0': 0.24; 'gets': 0.27; 'header:In-Reply-To:1': 0.27; 'function': 0.29; 'testing': 0.29; "doesn't": 0.30; 'code': 0.31; 'names.': 0.31; 'table': 0.34; 'could': 0.34; 'subject:with': 0.35; 'something': 0.35; 'objects': 0.35; 'test': 0.35; 'but': 0.35; 'accessing': 0.36; 'method': 0.36; 'charset:us-ascii': 0.36; 'subject:?': 0.36; 'being': 0.38; 'most': 0.60; 'name': 0.63; 'skip:n 10': 0.64; 'side': 0.67; 'frequently': 0.68; 'subject:there': 0.68; 'received:50.22': 0.84; 'subject:being': 0.84; 'to:addr:p': 0.84 Date: Tue, 3 Dec 2013 19:06:44 -0600 From: Tim Chase To: Piotr Dobrogost Subject: Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? In-Reply-To: References: <15912943-29a1-4365-b027-7bb8cec447f8@googlegroups.com> X-Mailer: Claws Mail 3.8.1 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - boston.accountservergroup.com X-AntiAbuse: Original Domain - python.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - tim.thechases.com X-Get-Message-Sender-Via: boston.accountservergroup.com: authenticated_id: tim@thechases.com 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: , Newsgroups: comp.lang.python Message-ID: Lines: 33 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1386119133 news.xs4all.nl 2928 [2001:888:2000:d::a6]:41047 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:60981 On 2013-12-03 15:47, Piotr Dobrogost wrote: > > The getattr function is meant for when your attribute name is in a > > variable. Being able to use strings that aren't valid identifiers > > is a side effect. > > Why do you say it's a side effect? I think random832 is saying that the designed purpose of setattr() was to dynamically set attributes by name, so they could later be accessed the traditional way; not designed from the ground-up to support non-identifier names. But because of the getattr/setattr machinery (dict key/value pairs), it doesn't prevent you from having non-identifiers as names as long as you use only the getattr/setattr method of accessing them. I see non-traditional-identifiers most frequently in test code where the globals() dictionary gets injected with various objects for testing purposes, driven by a table with descriptors. Something like (untested) tests = [ dict(desc="Test 1", input=10, expected=42), dict(desc="Test 2", input=314, expected=159), ] for test in tests: test_name = "test_" + test["desc"] globals()[test_name] = generate_test_function( test["input"], test["output"]) -tkc