An example of how to limit concurrent threads in Python

limit-concurrent-threads-python.py

import time
from threading import BoundedSemaphore, Thread


def main():
    max_num_threads = 100
    thread_limiter = BoundedSemaphore(max_num_threads)

    # OS's have limits on the number of threads that can be opened at once,
    # be aware of that with this number (eg: don't try something like 10,000+)
    # Using this method will spawn all threads at once but only run the number
    # of threads specified in `max_num_threads` at a given time
    for i in range(1000):
        Thread(
            target=print_string,
            args=(
                thread_limiter,
                i,
            )
        ).start()


def print_string(thread_limiter, i):
    try:
        thread_limiter.acquire()
        print('Hello World!' + str(i))
        time.sleep(1)
    finally:
        thread_limiter.release()


if __name__ == '__main__':
    main()