reading the last line of a file

[Martin Franklin]

Martin Franklin wrote:
> Xah Lee wrote:
> 
>>Martin Franklin wrote:
>>
>>
>>>import gzip
>>>log_file = gzip.open("access_log.4.gz")
>>>last_line = log_file.readlines()[-1]
>>>log_file.close()
>>
>>
>>does the
>>log_file.readlines()[-1]
>>actually read all the lines first?
> 
> 
> 
> Yes I'm afraid it does.
> 
> 
> 
>>i switched to system call with tail because originally i was using a
>>pure Python solution
>>
>>         inF = gzip.GzipFile(ff, 'rb');
>>         s=inF.readlines()
>>         inF.close()
>>         last_line=s[-1]
>>
>>and since the log file is 100 megabytes it takes a long time and hogs
>>massive memory.
>>
> 
> 
> Ok, in that case stick to your shell based solution, although 100
> megabytes does not sound that large to me I guess it is relative
> to the system you are running on :) (I have over a gig of memory here)
> 

And just a few minutes after I sent that... this...

import gzip

logfile = gzip.open("access_log.4.BIG.gz")

## seek relative to the end of the file
logfile.seek(-500)

last_line = logfile.readlines()[-1]

logfile.close()

print last_line


Works quite fast on my machine...

Regards
Martin