使用 Python 進行線程編程

1）使用 Python 進行線程編程, 研究了如何同時使用線程和隊列在 Python 中完成線程編程。

2） Queue — A synchronized queue class

The Queue module implements multi-producer, multi-consumer queues. It is especially useful in threaded programming when information must be exchanged safely between multiple threads. The Queue class in this module implements all the required locking semantics.

3） Queue – A thread-safe FIFO implementation，“It can be used to pass messages or other data between producer and consumer threads safely. Locking is handled for the caller, so it is simple to have as many threads as you want working with the same Queue instance.”
 

所以Queue對於調用者來說是安全執行緒的，可以放心的調用，下面給出一個例子。

 

          #!/usr/bin/env python
          import Queue
import threading
import urllib2
import time

          hosts = ["http://yahoo.com", "http://google.com", "http://amazon.com",
"http://ibm.com", "http://apple.com"]

          queue = Queue.Queue()

class ThreadUrl(threading.Thread):
"""Threaded Url Grab"""
def __init__(self, queue):
              threading.Thread.__init__(self)
              self.queue = queue

def run(self):
while True:
#grabs host from queue
                host = self.queue.get()

#grabs urls of hosts and prints first 1024 bytes of page
                url = urllib2.urlopen(host)
print url.read(1024)

#signals to queue job is done
                self.queue.task_done()

          start = time.time()
def main():

#spawn a pool of threads, and pass them queue instance 
            for i in range(5):
              t = ThreadUrl(queue)
              t.setDaemon(True)
              t.start()

#populate queue with data   
              for host in hosts:
                queue.put(host)

#wait on the queue until everything has been processed     
           queue.join()

          main()
print "Elapsed Time: %s" % (time.time() - start)