Python tail

tail.py

import os
import time
import sys


class Tail(object):

    def __init__(self, file_name):
        self.filename = file_name
        self.pos = 0

    def locate(self, line_to_print):
        with open(self.filename) as f:
            f.seek(0, os.SEEK_END)
            file_length = f.tell()
            n = 0
            while file_length > 0:
                pos = file_length - 1024
                pos = max(0, pos)
                f.seek(pos)
                buf = f.read(file_length - pos)
                count = 0
                for ch in buf[::-1]:
                    count += 1
                    if ch == '\n':
                        n += 1
                        if n > line_to_print:
                            self.pos = pos + len(buf) - count + 1
                            break
                file_length = pos

    def follow(self, n=5):
        self.locate(line_to_print=n)
        # print self.pos
        with open(self.filename) as f:
            f.seek(self.pos)
            while 1:
                line = f.readline()
                if line:
                    sys.stdout.write(line)
                else:
                    time.sleep(1)

if __name__ == "__main__":
    t = Tail("test.txt")
    t.follow(n=5)