from threading import Thread

var = 0

def inc_thread ():
    global var
    for _ in range (100000):
        var += 1

def dec_thread ():
    global var
    for _ in range (100000):
        var -= 1

def main():
    global var
    t2 = Thread (target = dec_thread)
    t1 = Thread (target = inc_thread)
    t2.start ()
    t1.start ()
    t1.join ()  # wait for the thread to finish
    t2.join ()
    print (var)

main()