最近引入了关于延迟处理能力以及实现“先进先出”等的队列设计。
查看文档,试图获取示例队列,以了解如何在我自己的设计/程序中实现它。但我在运行这段代码时遇到了问题:
import queue
def worker():
while True:
item = q.get()
do_work(item)
q.task_done()
def main():
q = queue.Queue(maxsize=0)
for i in range(num_worker_threads):
t = Thread(target=worker)
t.daemon = True
t.start()
for item in source():
q.put(item)
q.join() # block until all tasks are done
main()
问题:希望有人解释一下 for 循环在做什么,我在运行代码时遇到错误,所以我必须遗漏一些东西。
问题出现的错误:NameError:未定义全局名称“num_worker_threads”
来自 -Python 新手的感谢 -
for循环正在启动许多工作线程来执行“worker”定义的功能。以下是应在您的系统上运行 python 2.7 的工作代码。
import Queue
import threading
# input queue to be processed by many threads
q_in = Queue.Queue(maxsize=0)
# output queue to be processed by one thread
q_out = Queue.Queue(maxsize=0)
# number of worker threads to complete the processing
num_worker_threads = 10
# process that each worker thread will execute until the Queue is empty
def worker():
while True:
# get item from queue, do work on it, let queue know processing is done for one item
item = q_in.get()
q_out.put(do_work(item))
q_in.task_done()
# squares a number and returns the number and its square
def do_work(item):
return (item,item*item)
# another queued thread we will use to print output
def printer():
while True:
# get an item processed by worker threads and print the result. Let queue know item has been processed
item = q_out.get()
print "%d squared is : %d" % item
q_out.task_done()
# launch all of our queued processes
def main():
# Launches a number of worker threads to perform operations using the queue of inputs
for i in range(num_worker_threads):
t = threading.Thread(target=worker)
t.daemon = True
t.start()
# launches a single "printer" thread to output the result (makes things neater)
t = threading.Thread(target=printer)
t.daemon = True
t.start()
# put items on the input queue (numbers to be squared)
for item in range(10):
q_in.put(item)
# wait for two queues to be emptied (and workers to close)
q_in.join() # block until all tasks are done
q_out.join()
print "Processing Complete"
main()
每个 @handle 的 Python 3 版本
import queue
import threading
# input queue to be processed by many threads
q_in = queue.Queue(maxsize=0)
# output queue to be processed by one thread
q_out = queue.Queue(maxsize=0)
# number of worker threads to complete the processing
num_worker_threads = 10
# process that each worker thread will execute until the Queue is empty
def worker():
while True:
# get item from queue, do work on it, let queue know processing is done for one item
item = q_in.get()
q_out.put(do_work(item))
q_in.task_done()
# squares a number and returns the number and its square
def do_work(item):
return (item,item*item)
# another queued thread we will use to print output
def printer():
while True:
# get an item processed by worker threads and print the result. Let queue know item has been processed
item = q_out.get()
print("{0[0]} squared is : {0[1]}".format(item) )
q_out.task_done()
# launch all of our queued processes
def main():
# Launches a number of worker threads to perform operations using the queue of inputs
for i in range(num_worker_threads):
t = threading.Thread(target=worker)
t.daemon = True
t.start()
# launches a single "printer" thread to output the result (makes things neater)
t = threading.Thread(target=printer)
t.daemon = True
t.start()
# put items on the input queue (numbers to be squared)
for item in range(10):
q_in.put(item)
# wait for two queues to be emptied (and workers to close)
q_in.join() # block until all tasks are done
q_out.join()
print( "Processing Complete" )
main()
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