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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: Possible File iteration bug
Date: Fri, 15 Jul 2011 17:45:27 -0400
References: <ivnh2f$rdc$1@speranza.aioe.org>	<9f5ddd41-79a7-46a6-b5fe-dd94600d581a@j15g2000yqf.googlegroups.com> <ivpblc$qk4$1@speranza.aioe.org>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:9573

On 7/15/2011 8:26 AM, Billy Mays wrote:
> On 07/15/2011 04:01 AM, bruno.desthuilliers@gmail.com wrote:
>> On Jul 14, 9:46 pm, Billy Mays<no...@nohow.com> wrote:
>>> 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
>>
>> what's wrong with file.readlines() ?
>
> Using that will read the entire file into memory which may not be

So will getLines.

> possible. In the library reference, it mentions that using the generator
> (which calls file.next()) uses a read ahead buffer to efficiently loop
> over the file. If I call .readline() myself, I forfeit that performance
> gain.

Are you sure? Have you measured the difference?

-- 
Terry Jan Reedy