python 利用文件锁单例执行脚本的方法

#coding=utf-8
import fcntl, sys, time, os 
pidfile = 0 
 
def ApplicationInstance(): 
  global pidfile 
  pidfile = open(os.path.realpath(__file__), "r") 
  try: 
    fcntl.flock(pidfile, fcntl.LOCK_EX | fcntl.LOCK_NB) #创建一个排他锁,并且所被锁住其他进程不会阻塞 
  except: 
    print "another instance is running..." 
    sys.exit(1) 
 
if __name__ == "__main__": 
  ApplicationInstance() 
  while True: 
    print 'running...' 
    time.sleep(1)