Path: csiph.com!usenet.pasdenom.info!gegeweb.org!usenet-fr.net!nerim.net!novso.com!newsfeed.xs4all.nl!newsfeed4a.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 0.022 X-Spam-Evidence: '*H*': 0.96; '*S*': 0.00; 'from:addr:yahoo.co.uk': 0.04; 'matches': 0.07; 'assuming': 0.09; 'grid': 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; 'subject:How': 0.10; 'language.': 0.14; "wouldn't": 0.14; '"national': 0.16; 'frequencies': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'seconds.': 0.16; 'applies': 0.16; 'language': 0.16; 'wrote:': 0.18; 'seems': 0.21; '>>>': 0.22; 'header:User-Agent:1': 0.23; 'error': 0.23; 'certainly': 0.24; 'second': 0.26; 'world,': 0.26; 'header:X-Complaints-To:1': 0.27; 'header:In-Reply-To:1': 0.27; 'specified': 0.30; "i'm": 0.30; 'getting': 0.31; 'high.': 0.31; 'subject:that': 0.31; "we're": 0.32; 'limitation': 0.33; 'period': 0.33; 'subject:the': 0.34; 'could': 0.34; 'i.e.': 0.36; 'to:addr:python-list': 0.38; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'how': 0.40; 'dave': 0.60; 'save': 0.62; 'kind': 0.63; 'our': 0.64; 'more': 0.64; 'talking': 0.65; 'charset:windows-1252': 0.65; 'within': 0.65; 'hour': 0.70; 'power': 0.76; 'abnormal': 0.84; 'hour,': 0.84; 'nominal': 0.84; 'angel': 0.91; 'edwards': 0.91; 'obligation': 0.91; 'hundred': 0.95; 'period.': 0.95; 'kit': 0.97 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Mark Lawrence Subject: Re: How to terminate the function that runs every n seconds Date: Wed, 14 Jan 2015 17:54:00 +0000 References: <54B69A5B.5000801@davea.name> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit X-Gmane-NNTP-Posting-Host: host-92-24-222-48.ppp.as43234.net User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 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: 33 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1421258062 news.xs4all.nl 2832 [2001:888:2000:d::a6]:53303 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:83772 On 14/01/2015 17:37, Grant Edwards wrote: > On 2015-01-14, Mark Lawrence wrote: >> On 14/01/2015 16:33, Dave Angel wrote: >> >>> Note that neither Timer nor sleep makes any promises about how >>> accurately it matches the requested time. >> >> Reminds me of working on Telematics S200/300/4000/5000 telecomms kit in >> the early 90s where the timers were mains based, so a one hour timer >> would go off at about one hour, 30 seconds. > > I don't understand. Power line frequencies are _very_ accurate and > have been relied upon for timekeeping since the 1930s. We're talking > a few hundred PPM over a 24 hour period. A 30 second error over a one > hour period seems _really_ high. > From http://www2.nationalgrid.com/uk/services/balancing-services/frequency-response/ "National Grid has a licence obligation to control frequency within the limits specified in the 'Electricity Supply Regulations', i.e. ±1% of nominal system frequency (50.00Hz) save in abnormal or exceptional circumstances.". I wouldn't describe ±1% as very accurate and certainly not within a few hundred ppm. I'm assuming that this kind of limitation applies around the world, so could you be getting confused with some other more accurate frequency control? -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence