btbtbt

import threading
import time

mutex = threading.Lock()
sum = 0
sum2 = 0

def safe_race_thread1():
    global sum
    for i in range(0,1000):
        mutex.acquire()
        tmp = sum
        time.sleep(0)
        tmp += i
        time.sleep(0)
        sum = tmp
        mutex.release()

def safe_race_thread2():
    global sum
    for i in range(1, 1000):
        mutex.acquire()
        tmp = sum
        time.sleep(0)
        tmp -= i
        time.sleep(0)
        sum = tmp
        mutex.release()

def unsafe_race_thread1():
    global sum2
    for i in range(0, 1000):
        tmp = sum2
        time.sleep(0)
        tmp += i
        time.sleep(0)
        sum2 = tmp

def unsafe_race_thread2():
    global sum2
    for i in range(1, 1000):
        tmp = sum2
        time.sleep(0)
        tmp -= i
        time.sleep(0)
        sum2 = tmp

thread1 = threading.Thread(target = safe_race_thread1)
thread2 = threading.Thread(target = safe_race_thread2)
thread3 = threading.Thread(target = unsafe_race_thread1)
thread4 = threading.Thread(target = unsafe_race_thread2)
thread1.start()
thread2.start()
thread3.start()
thread4.start()
thread1.join()
thread2.join()
thread3.join()
thread4.join()
print ("Результат при работе с блокировкой", sum)
print ("Результат без блокировки", sum2)