python 锁机制

from lockfile import FileLock, AlreadyLocked, LockTimeout
LOCK_WAIT_TIMEOUT=1
lock=FileLock("/tmp/send_mail_sendmail")
print ('acquiring lock...')
try:
lock.acquire(LOCK_WAIT_TIMEOUT)
except AlreadyLocked:
print ("lock already in place. quitting.")
return
except LockTimeout:
print ("waiting for the lock timed out. quitting.")
return
print ("acquired.")
print ("releasing lock...")
lock.release()
print ("released.")