Searching string in (large) file.

[constntine]

I am working on a project and coding in Python 3.1 where I need to find a string in a file.

I have already considered reading the file to a string and then using rfind() on it, but that does not seem to be efficient, seeing as how I expect my file to be large.
I am considering using a for loop to read each line, but I'm not sure how efficient that is either.

Any better alternatives out there?

P.S. I need to find the last instance of the sub-string. So a bigger file will almost kill my previous method.

[TrustyTony]

You could seek to n KB from end of file, read n KB, if string found stop, otherwise seek n KB - search string length more behind, read n KB, .... until succeed or beginning is reached and string is not in file.

[woooee]

If you are confident that the string is not wrap-
ped around (on 2 lines), then reading the file one record at a time and searching it is the accepted way to go. You have to look at every character in the file no matter how you do it.

[snippsat]

Try with regex,and use an compile() regex with finditer() Look like this.

import re

text = """\
Hi,i have car.
I drive to work every day in my car.
This text will find all car,car.car?!car."""


r = re.compile(r'\b(car)\b')
for match in r.finditer(text):
    print match.group()