worker_manager.py

from threading import Thread, BoundedSemaphore

class Worker(Thread):
    def __init__(self, sema, target, args, kwargs):
        super(Worker, self).__init__()

        self.sema   = sema
        self.target = target
        self.args   = args
        self.kwargs = kwargs

    def run(self):
        self.sema.acquire()
        self.target(*self.args, **self.kwargs)
        self.sema.release()
        
class WorkerManager:

    def __init__(self, max_workers):
        self.worker_sema = BoundedSemaphore(max_workers)
    
    def queue_job(self, target, *args, **kwargs):
        thread = Worker(self.worker_sema, target, args, kwargs)
        thread.start()

if __name__ == '__main__':
    from string import lowercase
    from time import sleep

    def job(id):
        print id, 'is alive'
        
        for i in range(3):
            print id, i
            sleep(1)

        print id, 'dies'

    worker_manager = WorkerManager(5)

    for i in lowercase:    
        worker_manager.queue_job(job, i)