Python实现线程交替打印字符串

import threading
con = threading.Condition()
word = u"12345上山打老虎"

def work():
    global word
    con.acquire()
    while True:
        print word[0]
        word = word[1:]
        if len(word) == 0:
            break
        con.notify()
        if len(word) == 1:
            break
        con.wait()
    con.release()

t1 = threading.Thread(target=work)
t2 = threading.Thread(target=work)
t1.start()
t2.start()
t1.join()
t2.join()