Terminate all other threads if one succeeded

Question

Hi I'm trying to allow simultaneous testing of multiple words but I'm facing troubles with multithreading! Is it possible to terminate all other threads if one succeeded? Maybe I don't understand threading correctly! Pretty confused! Here is my code:

def testPass(hash, dname):
   dicFile = open(dname,'r')
   for word in dicFile.readlines():
      word = word.strip('\n')
      t = Thread(target=verifyWord, args=(hash, word))
      t.start()
   return

so I want to do something like if one of the t succeeded exit the loop. I don't know how to handle this.

score 2 · Answer 1 · edited May 23 '17 at 11:56

2

Forcing threads to terminate abruptly (i.e. killing them) is generally not a good idea - bad things can happen from a synchronization point of view.

You can achieve what you want by having all your threads checking a flag on a regular basis, telling them to terminate ASAP (but in a safe way) if the flag is set.

This answer should get you going nicely.

edited May 23 '17 at 11:56

Community

1
1

answered Jul 12 '13 at 12:13

Henrik

4,254
15
28

In that case how could it be done ? Because if the first word is correct it keeps verifying the remaining words in the dicfile. I don't want to check each word in the dicfile one at a time in the view of increasing performance. – Ze Kotch Jul 12 '13 at 12:59
Should be able to send a friendly signal (not sigkill, sigterm, etc.) to ask them to shut down cleanly, no? – ajwood Jul 12 '13 at 13:05

sebdelsol · Answer 2 · 2014-06-02T09:55:19.387

As suggested use a stop event that you regularly check in verifyWord, and set it when your task is done:

def verifyWord(hash,word,stopevent):

    #for every chunk of your computation, check that stopEvent is not set
    if not self.stopEvent.isSet():
        #do a part of your computation
    ...         

    #When you're done
    self.stopEvent.set()

Break out the for loop, when stopEvent has been set:

def testPass(hash, dname):

    stopEvent = threading.Event()

    dicFile = open(dname,'r')
    for word in dicFile.readlines():
        word = word.strip('\n')
        t = Thread(target=verifyWord, args=(hash, word,stopEvent))
        t.start()

        if stopEvent.isSet():
            break

Terminate all other threads if one succeeded

2 Answers2