OS assignment on threads (problem solved)

OS_assignment_threads_with_mutex.py

import threading
import time

var = 0
mutex = threading.Lock()

def runner0():
    i = 0
    global var
    while i < 1000000:
        mutex.acquire()
        var += 1
        mutex.release()
        i += 1

    print("Incrementation ended, var = %d" % var)
    return


def runner1():
    i = 0
    global var
    while i < 1000000:
        mutex.acquire()
        var -= 1
        mutex.release()
        i += 1
    print("Decrementation ended, var = %d" % var)
    return


# MAIN PART HERE #
start_time_seconds = time.time()
thread0 = threading.Thread(target=runner0, args=(), daemon=True)
thread1 = threading.Thread(target=runner1, args=(), daemon=True)
thread0.start()
thread1.start()
thread0.join()
thread1.join()
print("var = %d" % var)
print("Code took %.4f seconds to execute" % (time.time() - start_time_seconds))