Threadingで実行した関数の実行結果を呼び出し元で知るには

Queue.put()とQueue.getを使う．

import threading
import thread
from Queue import Queue

def threaded_func(a, b, q):
    #return a + b
    ret = a + b
    q.put(ret)

def main():
    q = Queue()
    th = threading.Thread(target=threaded_func, args=(1, 2, q))
    th.start()
    th.join()
    rslt = q.get()
    print rslt

if __name__ == '__main__':
    main()