[Tutor] Matching on multiple log lines

[Matthew Warren]

> -----Original Message-----
> From: tutor-bounces at python.org 
> [mailto:tutor-bounces at python.org] On Behalf Of Kent Johnson
> Sent: 30 October 2006 11:55
> Cc: tutor at python.org
> Subject: Re: [Tutor] Matching on multiple log lines
> 
> wesley chun wrote:
> >> so it's guaranteed that 'Writing Message to'
> >> will always be followed by 'TRANSPORT_STREAM_ID'
> >> before the next occurrence of 'Writing Message to'
> >> and all text between can be ignored,
> >> and we increment the counter if and only if
> >> there is a newline immediately after 'TRANSPORT_STREAM_ID'
> >> yes?
> > 
> > 
> > just throwing this out there... would anyone do something like a
> > open('log.txt', 'w').write(str(len(re.split(r'Writing Message
> > to([\w\d\s:/\.]+?)TRANSPORT_STREAM_ID    Parameter value:
> > 0160\r?\n'))), or is this unseemly due the fact that the file may be
> > very large?
> 
> If the log file can be read into memory then a regex-based solution 
> might work well though your code looks a bit scrambled to me. Rather 
> than re.split() I would use re.findall().
> 
> To solve this line-by-line I would make a simple state machine that 
> looks for lines of interest and moves through the states Begin, 
> Found_Transport_Stream_Id and Found_Writing_Message.
> 
> Kent

Exactly how I have solved this in the past writing a general purpose
tool for scanning logs for things. More code, but much easier to follow.

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