How to continue the program flow after one of several threads returns a value?

Question

In my program, there is a section where I utilize from multiple threads for simulating a distributed environment. All threads are trying to crack a password. As you can see, all threads call the same target function func with different arguments. This function returns a result whenever a trial that cracks the password is found.

def func(self, inp):
    trial = 0
    while (crackPwd(inp, trial) != True):
        trial += 1
    return inp

threads = []

for inp in range(inpAmount):
    thr = threading.Thread(target=func, args=(inp))
    threads.append(thr)
    thr.start()

for thr in threads:
    thr.join()

However what I want to do is to stop other threads after one of the threads cracks the password. I mean, I want to continue with the program flow after a thread returns a result from func(). I tried to find a solution but none of them seems to match my problem. Now, I got results from all threads and lose so much time waiting for all threads to finish. I will appreciate your help.

Answer 1

Could you use an instance of the threading Event class?

By mocking the crackPwd function mentioned in your code to sleep until the sleep_time is 10 seconds (with 10% probability) I tested with:

import time
import random
import threading

def crackPwd(inp, trial):
   sleep_time = random.randint(1, 10)
   time.sleep(sleep_time)
   return sleep_time

def func(inp):
   trial = 0
   while (crackPwd(inp, trial) != 10) and (not pwd_cracked.isSet()):
      trial += 1
   pwd_cracked.set()
   return inp

threads = []

for inp in range(10):
   pwd_cracked = threading.Event()
   thr = threading.Thread(target=func, args=(inp, ))
   threads.append(thr)
   thr.start()

for thr in threads:
   thr.join()

So for your original code:

def func(self, inp):
    trial = 0
    while (crackPwd(inp, trial) != True) and (not pwd_cracked.isSet()):
        trial += 1
    pwd_cracked.set()
    return inp

threads = []

for inp in range(inpAmount):
    pwd_cracked = threading.Event()
    thr = threading.Thread(target=func, args=(inp, ))
    threads.append(thr)
    thr.start()

for thr in threads:
    thr.join()