Python - How can I open a file and specify the offset in bytes?

Question

I\'m writing a program that will parse an Apache log file periodically to log it\'s visitors, bandwidth usage, etc..

The problem is, I don\'t want to open the log an

Answer 1

log = open('myfile.log')
pos = open('pos.dat','w')
print log.readline()
pos.write(str(f.tell())
log.close()
pos.close()

log = open('myfile.log')
pos = open('pos.dat')
log.seek(int(pos.readline()))
print log.readline()

Of course you shouldn't use it like that - you should wrap the operations up in functions like save_position(myfile) and load_position(myfile), but the functionality is all there.

Answer 2

If your logfiles fit easily in memory (this is, you have a reasonable rotation policy) you can easily do something like:

log_lines = open('logfile','r').readlines()
last_line = get_last_lineprocessed() #From some persistent storage
last_line = parse_log(log_lines[last_line:])
store_last_lineprocessed(last_line)

If you cannot do this, you can use something like (see accepted answer's use of seek and tell, in case you need to do it with them) Get last n lines of a file with Python, similar to tail