speed of string chunks file parsing

[MRAB]

Hyunchul Kim wrote:
> Hi, all
> 
> I have a simple script.
> Can you improve algorithm of following 10 line script, with a view point 
> of speed ?
> Following script do exactly what I want but I want to improve the speed.
> 
> This parse a file and accumulate lines till a line match a given regular 
> expression.
> Then, when a line match a given regular expression, this function yield 
> lines before the matched lines.
> 
> ****************
> import re
> resultlist = []
> cp_regularexpression = re.compile('^a complex regular expression here$)
> for line in file(inputfile):
>        if cp_regularexpression.match(line):
>                if resultlist != []:
>                        yield resultlist
>                        resultlist = []
>        resultlist.append(line)
> yield resultlist
> ****************
> 
> Thank you in advance,
> 
It looks OK to me.

Of course, it could be the regular expression that's the slowest part.
Have you tried timing it?