如何获取由特定类启动的活跃线程数量？

Question

代码如下：

class workers1(Thread):
    def __init__(self):
        Thread.__init__(self)
    def run(self):
        # ...do some stuff 

class workers2(Thread):
    def __init__(self):
        Thread.__init__(self)
    def run(self):
       # ...do some stuff 


if __name__ == "__main__":
    # start workers

while True: 
    print "Number of threads active", threading.activeCount()
    print "Number of worker1 threads", ?????, "Number of worker2 threads", ?????

有没有办法通过源类来获取活跃线程的数量？

Answer 1

你可以为每个类使用一个信号量，并获取它们的计数：请查看这个链接。

Answer 2

这是对Doug Hellman的多进程ActivePool示例代码的小改动（改成使用线程）。这个想法是让你的工作线程在一个池子里注册自己，完成后再注销自己，同时使用一个线程锁来协调对池子中活跃线程列表的修改：

import threading
import time
import random

class ActivePool(object):
    def __init__(self):
        super(ActivePool, self).__init__()
        self.active=[]
        self.lock=threading.Lock()
    def makeActive(self, name):
        with self.lock:
            self.active.append(name)
    def makeInactive(self, name):
        with self.lock:
            self.active.remove(name)
    def numActive(self):
        with self.lock:
            return len(self.active)
    def __str__(self):
        with self.lock:
            return str(self.active)
def worker(pool):
    name=threading.current_thread().name
    pool.makeActive(name)
    print 'Now running: %s' % str(pool)
    time.sleep(random.randint(1,3))
    pool.makeInactive(name)

if __name__=='__main__':
    poolA=ActivePool()
    poolB=ActivePool()    
    jobs=[]
    for i in range(5):
        jobs.append(
            threading.Thread(target=worker, name='A{0}'.format(i),
                             args=(poolA,)))
        jobs.append(
            threading.Thread(target=worker, name='B{0}'.format(i),
                             args=(poolB,)))
    for j in jobs:
        j.daemon=True
        j.start()
    while threading.activeCount()>1:
        for j in jobs:
            j.join(1)
            print 'A-threads active: {0}, B-threads active: {1}'.format(
                poolA.numActive(),poolB.numActive())

产生的结果是

Now running: ['A0']
Now running: ['B0']
Now running: ['A0', 'A1']
Now running: ['B0', 'B1']
 Now running: ['A0', 'A1', 'A2']
 Now running: ['B0', 'B1', 'B2']
Now running: ['A0', 'A1', 'A2', 'A3']
Now running: ['B0', 'B1', 'B2', 'B3']
Now running: ['A0', 'A1', 'A2', 'A3', 'A4']
Now running: ['B0', 'B1', 'B2', 'B3', 'B4']
A-threads active: 4, B-threads active: 5
A-threads active: 2, B-threads active: 5
A-threads active: 0, B-threads active: 3
A-threads active: 0, B-threads active: 3
A-threads active: 0, B-threads active: 3
A-threads active: 0, B-threads active: 3
A-threads active: 0, B-threads active: 3
A-threads active: 0, B-threads active: 0
A-threads active: 0, B-threads active: 0
A-threads active: 0, B-threads active: 0