#/usr/bin/env python
#-*- coding=utf-8 -*-

pos = 0
while True:
    con = open("a.txt")
    if pos != 0:
        con.seek(pos,0)
    while True:
	line = con.readline()
	if line.strip():
	    print line.strip()
	pos = pos + len(line)
	if not line.strip():
	    break
    con.close()

利用工具pyinotify監控文件內容變化，當文件逐漸變大時，可輕松完成任務：

#!/usr/bin/env python
#-*- coding=utf-8 -*-
import os
import datetime
import pyinotify
import logging

pos = 0
def printlog():
    global pos
    try:
        fd = open("log/a.txt")
	if pos != 0:
	    fd.seek(pos,0)
	while True:
	    line = fd.readline()
	    if line.strip():
	        print line.strip()
	    pos = pos + len(line)
	    if not line.strip():
		break
	fd.close()
    except Exception,e:
	print str(e)

class MyEventHandler(pyinotify.ProcessEvent):
    def process_IN_MODIFY(self,event):
        try:
	    printlog()
	except Exception,e:
	    print str(e)

def main():
    printlog()
    wm = pyinotify.WatchManager()
    wm.add_watch("log/a.txt",pyinotify.ALL_EVENTS,rec=True)
    eh = MyEventHandler()
    notifier = pyinotify.Notifier(wm,eh)
    notifier.loop()
if __name__ == "__main__":
    main()

Python監控文件內容變化