Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #9488

Re: Possible File iteration bug

Path csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!aioe.org!feeder.news-service.com!xlned.com!feeder7.xlned.com!newsfeed.xs4all.nl!newsfeed6.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
Return-Path <python-python-list@m.gmane.org>
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; 'else:': 0.03; 'subject:bug': 0.04; 'received:verizon.net': 0.07; 'terry': 0.07; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:80.91.229.12': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'received:lo.gmane.org': 0.09; 'wrote:': 0.15; "'rb')": 0.16; 'billy': 0.16; 'duplicates': 0.16; 'iterator.': 0.16; 'reedy': 0.16; 'pm,': 0.16; 'def': 0.16; 'written': 0.17; 'jan': 0.19; 'work,': 0.20; 'header:In-Reply- To:1': 0.22; 'noticed': 0.26; 'updated': 0.29; 'lines': 0.31; 'does': 0.32; 'to:addr:python-list': 0.34; 'header:X-Complaints- To:1': 0.34; 'header:User-Agent:1': 0.34; 'things': 0.34; 'skip:o 20': 0.36; 'file': 0.36; 'some': 0.37; 'using': 0.37; 'received:org': 0.38; 'subject:: ': 0.38; 'processing': 0.39; 'header:Mime-Version:1': 0.39; 'except': 0.39; 'to:addr:python.org': 0.39; 'look,': 0.84; 'subject:Possible': 0.84
X-Injected-Via-Gmane http://gmane.org/
To python-list@python.org
From Terry Reedy <tjreedy@udel.edu>
Subject Re: Possible File iteration bug
Date Thu, 14 Jul 2011 16:43:12 -0400
References <ivnh2f$rdc$1@speranza.aioe.org>
Mime-Version 1.0
Content-Type text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding 7bit
X-Gmane-NNTP-Posting-Host pool-74-109-121-73.phlapa.fios.verizon.net
User-Agent Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.18) Gecko/20110616 Lightning/1.0b2 Thunderbird/3.1.11
In-Reply-To <ivnh2f$rdc$1@speranza.aioe.org>
X-BeenThere python-list@python.org
X-Mailman-Version 2.1.12
Precedence list
List-Id General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe <http://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive <http://mail.python.org/pipermail/python-list>
List-Post <mailto:python-list@python.org>
List-Help <mailto:python-list-request@python.org?subject=help>
List-Subscribe <http://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups comp.lang.python
Message-ID <mailman.1037.1310676208.1164.python-list@python.org> (permalink)
Lines 34
NNTP-Posting-Host 2001:888:2000:d::a6
X-Trace 1310676208 news.xs4all.nl 23906 [2001:888:2000:d::a6]:47300
X-Complaints-To abuse@xs4all.nl
Xref x330-a1.tempe.blueboxinc.net comp.lang.python:9488

Show key headers only | View raw

On 7/14/2011 3:46 PM, Billy Mays wrote:
> I noticed that if a file is being continuously written to, the file
> generator does not notice it:

Because it does not look, as Ian explained.

> def getLines(f):
> lines = []
> for line in f:
> lines.append(line)
> return lines

This nearly duplicates .readlines, except for using f an an iterator.
Try the following (untested):

with open('/var/log/syslog', 'rb') as f:
   lines = f.readlines()
   # do some processing with lines
   # /var/log/syslog gets updated in the mean time
   lines = f.readlines()

People regularly do things like this with readline, so it is possible. 
If above does not work, try (untested):

def getlines(f):
   lines = []
   while True:
     l = f.readline()
     if l: lines.append(l)
     else: return lines

-- 
Terry Jan Reedy

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Possible File iteration bug Billy Mays <noway@nohow.com> - 2011-07-14 15:46 -0400
  Re: Possible File iteration bug Ian Kelly <ian.g.kelly@gmail.com> - 2011-07-14 14:00 -0600
    Re: Possible File iteration bug Billy Mays <noway@nohow.com> - 2011-07-14 16:15 -0400
      Re: Possible File iteration bug Hrvoje Niksic <hniksic@xemacs.org> - 2011-07-14 22:39 +0200
  Re: Possible File iteration bug Terry Reedy <tjreedy@udel.edu> - 2011-07-14 16:43 -0400
  Re: Possible File iteration bug "bruno.desthuilliers@gmail.com" <bruno.desthuilliers@gmail.com> - 2011-07-15 01:01 -0700
    Re: Possible File iteration bug Billy Mays <noway@nohow.com> - 2011-07-15 08:26 -0400
      Re: Possible File iteration bug Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2011-07-15 16:21 +0200
      Re: Possible File iteration bug Terry Reedy <tjreedy@udel.edu> - 2011-07-15 17:45 -0400
      Re: Possible File iteration bug Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-07-16 13:42 +1000
        Re: Possible File iteration bug Chris Angelico <rosuav@gmail.com> - 2011-07-16 14:07 +1000
        Re: Possible File iteration bug Cameron Simpson <cs@zip.com.au> - 2011-07-17 09:28 +1000
        Re: Possible File iteration bug Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2011-07-17 09:26 +0200
  Re: Possible File iteration bug Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2011-07-15 14:39 +0200
    Re: Possible File iteration bug Billy Mays <noway@nohow.com> - 2011-07-15 08:52 -0400
      Re: Possible File iteration bug Chris Angelico <rosuav@gmail.com> - 2011-07-15 22:58 +1000
      Re: Possible File iteration bug Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2011-07-15 16:28 +0200
        Re: Possible File iteration bug Billy Mays <81282ed9a88799d21e77957df2d84bd6514d9af6@myhashismyemail.com> - 2011-07-15 10:42 -0400
          Re: Possible File iteration bug Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2011-07-15 22:46 +0200
          Re: Possible File iteration bug Ethan Furman <ethan@stoneleaf.us> - 2011-07-15 14:20 -0700
          Re: Possible File iteration bug Terry Reedy <tjreedy@udel.edu> - 2011-07-15 17:47 -0400

csiph-web