Python: find regexp in a file

Question

Have:

f = open(...)  
r = re.compile(...)

Need:
Find the position (start and end) of a first matching regexp in a big file?
(star

Answer 1

The following code works reasonably well with test files around 2GB in size.

def search_file(pattern, filename, offset=0):
    with open(filename) as f:
        f.seek(offset)
        for line in f:
            m = pattern.search(line)
            if m:
                search_offset = f.tell() - len(line) - 1
                return search_offset + m.start(), search_offset + m.end()

Note that the regular expression must not span multiple lines.