Python線程代碼不起作用

Question

為什么此代碼“操作”未穿線？ （請參閱輸出。）

import time
from threading import Thread

def main():
    for nums in [range(0,5), range(5,10)]:
        t = Spider(nums)
        t.start()
        print 'started a thread'
        t.join()
    print "done"

class Spider(Thread):
    def __init__(self, nums):
        Thread.__init__(self)
        self.nums = nums
    def run(self):  # this is an override
        for num in self.nums:
            time.sleep(3)  # or do something that takes a while
            print 'finished %s' % (num, )

if __name__ == '__main__':
    main()

輸出：

started a thread
finished 0
finished 1
finished 2
finished 3
finished 4
started a thread
finished 5
finished 6
finished 7
finished 8
finished 9
done

Answer 1

說t.join() ，是在告訴它等待線程結束。

這意味着，您要讓它創建一個線程，啟動它，然后等待線程結束，然后再創建一個新線程。

如果您希望它充當多線程，則需要將join()移到循環之外。

def main():
    # We will store the running threads in this
    threads = []
    # Start the threads
    for nums in [range(0,5), range(5,10)]:
        t = Spider(nums)
        t.start()
        print 'started a thread'
        threads.append(t)
    # All the threads have been started
    # Now we wait for them to finish
    for t in threads:
        t.join()
    print "done"

也可以看看：

• Thread.join()文檔

Answer 2

您的線程連接t.join阻塞主線程，直到該線程完成執行（ http://docs.python.org/library/threading.html#threading.Thread.join ）。 更改代碼，使其看起來像這樣：

def main():
  threads = [] 
  for nums in [range(0,5), range(5,10)]:
    t = Spider(nums)
    t.start()
    print 'started a thread'
    threads.append(t)
  for t in threads: t.join()
  print "done"

Answer 3

您需要先啟動兩個線程，然后在它們都運行后再加入它們。