#!/usr/bin/env python3

from time import sleep

def tail (filename, n=0, polling=0.01):
  num_lines = sum(1 for line in open(filename))
  f = open(filename,'r')
  cpt = 0
  while cpt < num_lines - n :
    cpt += 1
    next(f)

  try:
    while True:
      try:
        l = next(f)
        print(filename,":",l[:-1])
      except:
        sleep(polling)
  except:
    f.close()