Readers_writers_problem

from random import shuffle, randint
import threading
from time import sleep

size = 1000
resource = [0 for _ in range(size)]

mutexes = [threading.Lock() for _ in range(size)]
reader_mutex = [threading.Lock() for _ in range(size)]
reader_amount = [0 for _ in range(size)]


def reader():

    while True:
        index = randint(0, size-1)
        with reader_mutex[index]:
            reader_amount[index] += 1

            if reader_amount[index] == 1:
                mutexes[index].acquire()

            print(f'Read value {resource[index]}')

        with reader_mutex[index]:
            reader_amount[index] -= 1
            if reader_amount[index] == 0:
                mutexes[index].release()
        sleep(2)


def writer():

    while True:
        index = randint(0, size-1)

        mutexes[index].acquire()
        value = randint(0, 100)
        resource[index] = value
        print(f'Write value {value}')

        mutexes[index].release()
        sleep(2)


def main():
    threads = [threading.Thread(target=reader) for _ in range(
        4)] + [threading.Thread(target=writer) for _ in range(4)]
    shuffle(threads)

    for thread in threads:
        thread.start()


if __name__ == '__main__':
    main()