Path: csiph.com!usenet.pasdenom.info!news.redatomik.org!newsfeed.xs4all.nl!newsfeed1.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 0.003 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'binary': 0.05; 'mrab': 0.05; 'feature.': 0.07; 'nicely': 0.07; 'seemed': 0.07; 'subject:How': 0.09; '[1,': 0.09; ']))': 0.09; 'bits.': 0.09; 'integers': 0.09; 'loop.': 0.09; 'python': 0.11; 'algorithm': 0.13; 'question.': 0.13; 'bits,': 0.16; 'expands': 0.16; 'wrote:': 0.16; 'string': 0.17; 'integer': 0.18; '>>>': 0.20; 'bit': 0.23; "haven't": 0.24; 'header:In-Reply-To:1': 0.24; 'header:User- Agent:1': 0.26; 'converting': 0.27; 'becomes': 0.31; 'e.g.': 0.31; 'help,': 0.32; 'subject:lists': 0.32; 'problem': 0.33; 'everyone.': 0.33; 'int': 0.33; 'lists': 0.34; 'to:addr:python- list': 0.35; 'done': 0.35; 'question,': 0.35; 'list': 0.35; 'asking': 0.35; 'but': 0.36; 'being': 0.36; 'text': 0.36; 'there': 0.36; 'thanks': 0.36; 'subject:: ': 0.37; 'thought': 0.37; 'rather': 0.38; 'doing': 0.38; 'offered': 0.38; 'wanted': 0.39; 'to:addr:python.org': 0.39; 'received:192': 0.39; 'some': 0.40; 'back': 0.61; 'john': 0.61; 'genuine': 0.63; 'great': 0.64; 'forward': 0.65; 'decided': 0.65; 'charset:windows-1252': 0.65; 'homework': 0.84; 'replies.': 0.84; 'route': 0.84; 'years!': 0.84 Date: Sat, 30 May 2015 00:18:02 +0100 From: John Pote User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: python-list@python.org Subject: Re: How to do integers to binary lists and back References: <33677AE8-B2FA-49F9-9304-C8D93784255D@gmail.com> <8A3659BC-9100-4A3A-9117-47227B3D290B@gmail.com> <5522439B-AEFA-400D-9B6F-00613528381F@gmail.com> <555E5A44.20006@o2.co.uk> <555E5CD8.4090704@mrabarnett.plus.com> In-Reply-To: <555E5CD8.4090704@mrabarnett.plus.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.20+ 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: 49 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1432941587 news.xs4all.nl 2913 [2001:888:2000:d::a6]:60861 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:91510 On 21/05/2015 23:31, MRAB wrote: > On 2015-05-21 23:20, John Pote wrote: >> Hi everyone. >> I recently had the problem of converting from an integer to its >> representation as a list of binary bits, each bit being an integer 1 or >> 0, and vice versa. E.G. >> 0x53 >> becomes >> [ 0, 1, 0, 1, 0, 0, 1, 1 ] >> >> This I wanted to do for integers of many tens, if not hundreds, of bits. >> Python very nicely expands integers to any size required, great feature. >> >> Just wondered if there was a neat way of doing this without resorting to >> a bit bashing loop. >> >> Looking forward to some interesting answers, >> John >> >> > I don't know how efficient you want it to be, but: > > >>> number = 0x53 > >>> bin(number) > '0b1010011' > >>> bin(number)[2 : ] > '1010011' > >>> list(map(int, bin(number)[2 : ])) > [1, 0, 1, 0, 0, 1, 1] > Thanks for the replies. Interesting that the offered solutions involve converting to a binary text string and then the individual chars back to ints. I had thought this would be a route to solve this problem but it seemed a bit 'heavy' hence I thought it worthwhile asking the question. My solution to converting a list of 1s and 0s back to an int is listLen = len( binList ) n = sum( [ binList[i]*( 2**(listLen-1 - i) ) for i in range(listLen)] ) In response to Ben Finney's question, I haven't done homework for 40 years! Genuine problem, I had decided that the clearest way to write the algorithm I was working on was to use lists of 1s and 0s rather than normal ints. Thanks for the help, John