'''
【线程冲突】示例：
多个线程并发访问同一个变量而互相干扰
互斥锁
    状态：锁定/非锁定
    #创建锁
        lock = threading.Lock()
    #锁定
        lock.acquire()
    #释放
        lock.release()
'''

import threading

import time

money = 0


# CPU分配的时间片不足以完成一百万次加法运算，
# 因此结果还没有被保存到内存中就被其它线程所打断
def addMoney():
    global money
    for i in range(1000000):
        money += 1
    print(money)


# 创建线程锁
lock = threading.Lock()


def addMoneyWithLock():
    # print("addMoneyWithLock")
    time.sleep(1)
    global money
    # print(lock.acquire())
    # if lock.acquire():
    #     for i in range(1000000):
    #         money += 1
    # lock.release()
    # 独占线程锁
    with lock:  # 阻塞直到拿到线程锁

        # -----下面的代码只有拿到lock对象才能执行-----
        for i in range(1000000):
            money += 1
        # 释放线程锁，以使其它线程能够拿到并执行逻辑
        # ----------------锁已被释放-----------------

    print(money)


# 5条线程同时访问money变量，导致结果不正确
def conflictDemo():
    for i in range(5):
        t = threading.Thread(target=addMoney)
        t.start()


# 通过线程同步（依次执行）解决线程冲突
def handleConflictBySync():
    for i in range(5):
        t = threading.Thread(target=addMoney)
        t.start()
        t.join()  # 一直阻塞到t运行完毕


# 通过依次独占线程锁解决线程冲突
def handleConflictByLock():
    # 并发5条线程
    for i in range(5):
        t = threading.Thread(target=addMoneyWithLock)
        t.start()


if __name__ == '__main__':
    # conflictDemo()
    # handleConflictBySync()
    handleConflictByLock()

    pass