Python線程代碼不起作用線程

Question

爲什麼此代碼沒有「行爲」線程化？ （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

當你說t.join()，你告訴它等待線程結束。

這意味着，您要求它創建一個線程，啓動它，然後等待線程結束後再創建一個新線程。

如果您希望它執行多線程操作，您需要將join()移到循環外部。

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" 

參見：

• Documentation of Thread.join()

Answer 2

您需要先啓動兩個線程，然後和他們在一起，一旦他們都在運行。

Answer 3

您的主題加入t.join會阻塞主線程，直到線程完成執行（http://docs.python.org/library/threading.html#threading.Thread.join）。將代碼更改爲如下所示：

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"