Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.fsmpi.rwth-aachen.de!rt.uk.eu.org!newsfeed.xs4all.nl!newsfeed4.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 0.006 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'variables': 0.07; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'python': 0.11; '2.7': 0.14; '10000000': 0.16; 'assignments': 0.16; 'losing': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'tuple': 0.16; 'variables,': 0.16; 'wrote:': 0.18; 'machine': 0.22; 'header:User-Agent:1': 0.23; 'this:': 0.26; 'skip:" 20': 0.27; 'header:X-Complaints-To:1': 0.27; 'header:In- Reply-To:1': 0.27; 'related': 0.29; "doesn't": 0.30; 'start,': 0.30; 'code': 0.31; 'end,': 0.31; 'subject:some': 0.31; 'skip:c 30': 0.32; 'skip:- 30': 0.32; 'but': 0.35; 'method': 0.36; 'similar': 0.36; 'to:addr:python-list': 0.38; 'skip:- 10': 0.38; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'simple': 0.61; 'received:109': 0.72; 'faster.': 0.84; 'joel': 0.91; 'write:': 0.91 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Robin Becker Subject: Re: squeeze out some performance Date: Mon, 09 Dec 2013 15:54:36 +0000 References: <9df6ccd7-828d-43be-ac49-fe1c6a38bae7@googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Gmane-NNTP-Posting-Host: 109.174.168.73 User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:24.0) Gecko/20100101 Thunderbird/24.1.1 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: 37 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1386604487 news.xs4all.nl 2971 [2001:888:2000:d::a6]:46964 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:61392 On 06/12/2013 22:07, Joel Goldstick wrote: .......... >> > > Not that this will speed up your code but you have this: > > if not clockwise: > s = start > start = end > end = s > > Python people would write: > end, start = start, end this works for some small number of variables, but on my machine with python 2.7 I start losing with 4 variables eg > C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4" "a,b,c,d=b,c,d,a" > 1000000 loops, best of 3: 0.206 usec per loop > > C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4" "t=a;a=b;b=c;c=d;d=t" > 10000000 loops, best of 3: 0.118 usec per loop It doesn't seem to make much difference that the variables are related as I see a similar behaviour for simple assignments > C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4;e=5;f=6;g=7;h=8" "a,b,c,d=e,f,g,h" > 1000000 loops, best of 3: 0.204 usec per loop > > C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4;e=5;f=6;g=7;h=8" "a=e;b=f;c=g;d=h" > 10000000 loops, best of 3: 0.103 usec per loop for less than 4 variables the tuple method is faster. -- Robin Becker