tail in python

tail.py

import sys
import time

def tail(tfile):
    with open(tfile, 'r') as fp:
        while True:
            ll = fp.readline()
            if ll:
                print ll
            else:
                time.sleep(0.5)


if __name__ == "__main__":
    if len(sys.argv) < 2:
        print "tail.py <file>"
        sys.exit()
    tail (sys.argv[1])