一个错误的例子-来自parallel programming with python

该例子就是parallel_fibonacci.py.
每次跑有时候能获取到一个结果，有时候一个结果也获取不到。

import logging,threading
import time
from queue import Queue

logger=logging.getLogger()
logger.setLevel(logging.DEBUG)

formatter=logging.Formatter('%(asctime)s-%(message)s')

ch=logging.StreamHandler()
ch.setLevel(logging.DEBUG)
ch.setFormatter(formatter)
logger.addHandler(ch)

fibo_dict={}
shared_queue=Queue()
input_list=[3,10,5,7]

queue_condition=threading.Condition()

def fibonacci_task(condition):
    with condition:
        while shared_queue.empty():
            logger.info("[%s] -waiting for elements in queue..."
                %threading.current_thread().name)
            condition.wait()
        else:
            value=shared_queue.get()
            a,b=0,1
            for item in range(value):
                a,b=b,a+b
                fibo_dict[value]=a
        shared_queue.task_done()
    with condition:
        while shared_queue.empty():
            logger.info("[%s] -waiting for elements in queue..."
                %threading.current_thread().name)
            condition.wait()
        else:
            value=shared_queue.get()
            a,b=0,1
            for item in range(value):
                a,b=b,a+b
                fibo_dict[value]=a
        shared_queue.task_done()
        logger.debug("[%s] fibonacci of key [%d] with result [%d]"
                %(threading.current_thread().name,value,fibo_dict[value]))

def queue_task(condition):
    logging.debug('Starting queue_task...')
    with condition:
        for item in input_list:
            shared_queue.put(item)
        logging.debug('Notifying fibonacci_task threads\
            that the queue is ready to consume..')
        condition.notifyAll()

threads=[threading.Thread(daemon=True,target=fibonacci_task,
    args=(queue_condition,)) for i in range(4)]

[thread.start() for thread in threads]

prod=threading.Thread(name='queue_task_thread',daemon=True,
    target=queue_task,args=(queue_condition,))
prod.start()
#prod.join()
#time.sleep(10)
[thread.join for thread in threads]

出错的理由如下：
Daemonic threads can’t be joined. However, they are destroyed automatically when the main thread terminates.
把threads 语句中daemon=True 改成了False 就能得到正确的结果