Precompiled regular expressions slower?

[Simon Brunning]

> From:	Peter Bienstman [SMTP:pbienst at mit.edu]
> I've a Python script a want to optimise. It basically loops over all the 
> lines in a file and does some regular expression matching:
> 
> line = inputfile.readline()
> while line:
>   s = search(r".....", line)
>   ...
>   line = inputfile.readline()
 
You might find something like this faster:

for line in inputfile.xreadlines():
    s = search(r".....", line)
    ...
 
> There are several reg ex in the loop. Since the Python version runs 2 to 3
> 
> times as slow as its Perl counterpart, I thought I'd try speeding up the 
> script by precompiling the reg ex:
> 
> re1 = compile(r"....") 
> ...
> line = inputfile.readline()
> while line:
>   s = search(re1, line)
>   ...
>   line = inputfile.readline()
> 
> 
> Strangely enough this new version seems to run about 30% *slower* than the
> 
> old version.
 
Try putting the whole lot in a function - global access is slower than local
access.

Cheers,
Simon Brunning
TriSystems Ltd.
sbrunning at trisystems.co.uk




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