Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!news.mixmin.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 0.000 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'from:addr:yahoo.co.uk': 0.04; "'a'": 0.09; 'false,': 0.09; 'false.': 0.09; 'lawrence': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'type,': 0.09; 'language.': 0.14; '"and"': 0.16; "'b',": 0.16; '0))': 0.16; "['a',": 0.16; 'bitwise': 0.16; 'bool': 0.16; 'boolean': 0.16; 'dict': 0.16; 'operators.': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'simplified': 0.16; 'subject:expression': 0.16; "{'a':": 0.16; 'language': 0.16; 'wrote:': 0.18; 'alex': 0.19; 'aug': 0.22; 'putting': 0.22; 'header:User-Agent:1': 0.23; 'finally,': 0.24; "shouldn't": 0.24; 'this:': 0.26; 'second': 0.26; 'header:X-Complaints-To:1': 0.27; 'van': 0.27; 'header:In-Reply-To:1': 0.27; "d'aprano": 0.31; 'operators': 0.31; 'steven': 0.31; 'probably': 0.32; 'fri,': 0.33; 'third': 0.33; 'something': 0.35; 'case,': 0.35; 'equal': 0.35; 'there': 0.35; 'subject:?': 0.36; 'generic': 0.38; 'to:addr :python-list': 0.38; 'rather': 0.38; 'does': 0.39; 'bad': 0.39; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'called': 0.40; 'how': 0.40; 'expression': 0.60; "you're": 0.61; 'first': 0.61; 'our': 0.64; 'charset:windows-1252': 0.65; 'together,': 0.84 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Mark Lawrence Subject: Re: dict to boolean expression, how to? Date: Fri, 01 Aug 2014 16:50:51 +0100 References: <53db8bd8$0$2976$e4fe514c@news2.news.xs4all.nl> <53db95e6$0$29986$c3e8da3$5496439d@news.astraweb.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Gmane-NNTP-Posting-Host: host-78-147-28-172.as13285.net User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.0 In-Reply-To: <53db95e6$0$29986$c3e8da3$5496439d@news.astraweb.com> 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: 45 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1406908269 news.xs4all.nl 2917 [2001:888:2000:d::a6]:57452 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:75490 On 01/08/2014 14:28, Steven D'Aprano wrote: > On Fri, 01 Aug 2014 12:45:12 +0000, Alex van der Spek wrote: > >> With a dict like so: >> >> cond = {'a': 1, 'b': 1, 'c': 1, >> 'A': 0, 'B', 0, 'C':0} >> >> how would you make a boolean expression like this: >> >> bool = (('a' == 1) & ('A' == 0) | >> ('b' == 1) & ('B' == 0) | >> ('c' == 1) & ('C' == 0)) > > That's False. It's always False, because 'a' does not equal 1, etc. Also, > you're using bitwise operators & and | rather than boolean operators. > Finally, you are shadowing the built-in bool() type, which is probably a > bad idea. > > In the first case, I think you mean cond['a'] == 1 rather than just > 'a'==1; in the second case, the bool operators are called "and" and "or"; > and in the third case, there are many equally good names for a generic > boolean flag, like "flag". > > Putting those together, I think you probably mean something like this: > > flag = ( > (cond['a'] == 1 and cond['A'] == 0) or > (cond['b'] == 1 and cond['B'] == 0) or > (cond['c'] == 1 and cond['C'] == 0) > ) > > which can be simplified to: > > flag = any( cond[c] == 1 and cond[c.upper()] for c in ['a', 'b', 'c'] ) > Shouldn't that be cond[c.upper()] == 0 ? -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence