#!/usr/bin/env python
# -*- coding: utf-8 -*-import threading
import timeshared_resource_with_lock = 0
shared_resource_with_no_lock = 0
COUNT = 100000
shared_resource_lock = threading.Lock()class Box(object):lock = threading.RLock()def __init__(self):self.total_items = 0def execute(self, n):Box.lock.acquire()self.total_items += nBox.lock.release()def add(self):Box.lock.acquire()self.execute(1)Box.lock.release()def remove(self):Box.lock.acquire()self.execute(-1)Box.lock.release()def adder(box, items):while items > 0:print("adding 1 item in the box\n")box.add()time.sleep(5)items -= 1def remover(box, items):while items > 0:print("removing 1 item in the box")box.remove()time.sleep(5)items -= 1def increment_with_lock():global shared_resource_with_lockfor i in range(COUNT):shared_resource_lock.acquire()shared_resource_with_lock += 1shared_resource_lock.release()def decrement_with_lock():global shared_resource_with_lockfor i in range(COUNT):shared_resource_lock.acquire()shared_resource_with_lock -= 1shared_resource_lock.release()def increment_without_lock():global shared_resource_with_no_lockfor i in range(COUNT):shared_resource_with_no_lock += 1def decrement_without_lock():global shared_resource_with_no_lockfor i in range(COUNT):shared_resource_with_no_lock -= 1if __name__ == "__main__":t1 = threading.Thread(target = increment_with_lock)t2 = threading.Thread(target = decrement_with_lock)t3 = threading.Thread(target = increment_without_lock)t4 = threading.Thread(target = decrement_without_lock)t1.start()t2.start()t3.start()t4.start()t1.join()t2.join()t3.join()t4.join()print ("the value of shared variable with lock management is %s"\%shared_resource_with_lock)print ("the value of shared variable with race condition is %s"\%shared_resource_with_no_lock)items = 5print("putting %s items in the box " % items)box = Box()t1 = threading.Thread(target=adder, args=(box, items))t2 = threading.Thread(target=remover, args=(box, items))t1.start()t2.start()t1.join()t2.join()print ("%s items still remain in the box " % box.total_items)