Possible File iteration bug

From	Billy Mays <noway@nohow.com>
Newsgroups	comp.lang.python
Subject	Possible File iteration bug
Date	2011-07-14 15:46 -0400
Organization	Aioe.org NNTP Server
Message-ID	<ivnh2f$rdc$1@speranza.aioe.org> (permalink)

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I noticed that if a file is being continuously written to, the file 
generator does not notice it:



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

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

     # always returns an empty list, even though f has more data
     lines = getLines(f)




I found a workaround by adding f.seek(0,1) directly before the last 
getLines() call, but is this the expected behavior?  Calling f.tell() 
right after the first getLines() call shows that it isn't reset back to 
0.  Is this correct or a bug?

--
Bill

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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

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