The right way to limit maximum number of threads running at once?

Question

I\'d like to create a program that runs multiple light threads, but limits itself to a constant, predefined number of concurrent running tasks, like this (but with no risk o

Answer 1

For apply limitation on thread creating, follow this example (it really works):

import threading
import time


def some_process(thread_num):
    count = 0
    while count < 5:
        time.sleep(0.5)
        count += 1
        print "%s: %s" % (thread_num, time.ctime(time.time()))
        print 'number of alive threads:{}'.format(threading.active_count())


def create_thread():
    try:
        for i in range(1, 555):  # trying to spawn 555 threads.
            thread = threading.Thread(target=some_process, args=(i,))
            thread.start()

            if threading.active_count() == 100:  # set maximum threads.
                thread.join()

            print threading.active_count()  # number of alive threads.

    except Exception as e:
        print "Error: unable to start thread {}".format(e)


if __name__ == '__main__':
    create_thread()

Or:

Another way to set a thread number checker mutex/lock such as below example:

import threading
import time


def some_process(thread_num):
    count = 0
    while count < 5:
        time.sleep(0.5)
        count += 1
        # print "%s: %s" % (thread_num, time.ctime(time.time()))
        print 'number of alive threads:{}'.format(threading.active_count())


def create_thread2(number_of_desire_thread ):
    try:
        for i in range(1, 555):
            thread = threading.Thread(target=some_process, args=(i,)).start()

            while number_of_desire_thread <= threading.active_count():
                '''mutex for avoiding to additional thread creation.'''
                pass

            print 'unlock'
            print threading.active_count()  # number of alive threads.

    except Exception as e:
        print "Error: unable to start thread {}".format(e)


if __name__ == '__main__':
    create_thread2(100)