Python如何以结束线程的方式结束函数（即减少线程.activeCount（）乘以1）？

Question

我刚开始尝试一种同时下载多个文件的线程方式。我的实现使用thread.start_new_线程(). 在

我想一次下载10个文件，然后等待所有10个文件完成下载，然后再开始下10个文件。在我下面的代码中，线程.activeCount（）永远不会减少，即使download（）以exit（）结束，系统出口（）或返回。在

我的解决方法是引入downloadsRemaining计数器，但是现在活动线程的数量不断增加。在下面的示例程序的末尾，将有500个活动线程，我一次只需要10个线程。在

import urllib
import thread
import threading
import sys

def download(source, destination):

    global threadlock, downloadsRemaining

    audioSource = urllib.urlopen(source)
    output = open(destination, "wb")
    output.write(audioSource.read())
    audioSource.close()
    output.close()

    threadlock.acquire()
    downloadsRemaining = downloadsRemaining - 1
    threadlock.release()

    #exit()
    #sys.exit()    None of these 3 commands decreases threading.activeCount()
    #return


for i in range(50):
    downloadsRemaining = 10
    threadlock = thread.allocate_lock()

    for j in range(10):
        thread.start_new_thread(download, (sourceList[i][j], destinationList[i][j]))

    #while threading.activeCount() > 0:  <<<I really want to use this line rather than the next
    while downloadsRemaining > 0:
        print "NUMBER ACTIVE THREADS:  " + str(threading.activeCount())
        time.sleep(1)

Answer 1

根据the documentation：

Start a new thread and return its identifier. The thread executes the function function with the argument list args (which must be a tuple). The optional kwargs argument specifies a dictionary of keyword arguments. When the function returns, the thread silently exits. When the function terminates with an unhandled exception, a stack trace is printed and then the thread exits (but other threads continue to run).

（着重强调）

所以当函数返回时线程应该退出。在