how to get the return value of a thread?

Fredrik Lundh fredrik at
Fri Sep 9 14:37:25 CEST 2005

Leo Jay wrote:

> i would like to get the return value of all threads
> e.g.
> def foo(num):
>    if num>10:
>        return 1
>    elif num>50:
>        return 2
>    else
>        return 0
> after i invoked
> t = thread.start_new_thread(foo,(12,))
> how to get the return value of `foo'?

threads are subprograms, not functions.  to allow a thread to generate values,
create a shared Queue object and let your threads add stuff to that queue.  an

import threading
import Queue
import time, random

class Worker(threading.Thread):

    def __init__(self, index, queue):
        self.__index = index
        self.__queue = queue

    def run(self):
        # pretend we're doing something that takes 10-100 ms
        time.sleep(random.randint(10, 100) / 1000.0)
        # pretend we came up with some kind of value
        self.__queue.put((self.__index, random.randint(0, 1000)))

queue = Queue.Queue()

for i in range(10):
    Worker(i, queue).start() # start a worker

for i in range(10):
    print "worker %d returned %d" % queue.get()


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