How to manage python threads results?

I am using this code:

def startThreads(arrayofkeywords):
    global i
    i = 0
    while len(arrayofkeywords):
        try:
            if i<maxThreads:
                keyword = arrayofkeywords.pop(0)
                i = i+1
                thread = doStuffWith(keyword)
                thread.start()
        except KeyboardInterrupt:
            sys.exit()
    thread.join()

for threading in python, I have almost everything done, but I dont know how to manage the results of each thread, on each thread I have an array of strings as result, how can I join all those arrays into one safely? Because, I if I try writing into a global array, two threads could be writing at the same time.