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  • python系统编程(七)

     

    多线程-共享全局变量

    from threading import Thread
    import time
    
    g_num = 100
    
    def work1():
        global g_num
        for i in range(3):
            g_num += 1
    
        print("----in work1, g_num is %d---"%g_num)
    
    
    def work2():
        global g_num
        print("----in work2, g_num is %d---"%g_num)
    
    
    print("---线程创建之前g_num is %d---"%g_num)
    
    t1 = Thread(target=work1)
    t1.start()
    
    #延时一会,保证t1线程中的事情做完
    time.sleep(1)
    
    t2 = Thread(target=work2)
    t2.start()

    列表当做实参传递到线程中

    from threading import Thread
    import time
    
    def work1(nums):
        nums.append(44)
        print("----in work1---",nums)
    
    
    def work2(nums):
        #延时一会,保证t1线程中的事情做完
        time.sleep(1)
        print("----in work2---",nums)
    
    g_nums = [11,22,33]
    
    t1 = Thread(target=work1, args=(g_nums,))
    t1.start()
    
    t2 = Thread(target=work2, args=(g_nums,))
    t2.start()

    总结:

    • 在一个进程内的所有线程共享全局变量,能够在不适用其他方式的前提下完成多线程之间的数据共享(这点要比多进程要好)
    • 缺点就是,线程是对全局变量随意遂改可能造成多线程之间对全局变量的混乱(即线程非安全)
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  • 原文地址:https://www.cnblogs.com/leecoffee/p/9036905.html
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