Python efficient way to check if very large string contains a substring

Question

Python is not my best language, and so I\'m not all that good at finding the most efficient solutions to some of my problems. I have a very large string (coming from a 30 MB

Answer 1

I would rely on fast implementation by someone else:

import subprocess
from subprocess import STDOUT
import os

...
with open(os.devnull, 'w') as devnull:
    if subprocess.call('grep %s "%s"' % (smallstring, file), shell=True, stdout=devnull, stderr=STDOUT) == 0:
        pass #do stuff

Won't work on windows.

edit: I'm worried taht grep returns 0 wheter it finds something or not. But I don't have any shell available to me now so I can't test it.