Python学习笔记23：多线程

import time
import threading
loop = [4, 2]
class ThreadFunc:
    def __init__(self, name):
        self.name = name
    def loop(self, nloop, nsec):
        #nloop:loop函数的名称
        #nsec:系统休眠时间
        print('Start loop', nloop, 'at', time.ctime())
        sleep(nsec)
        print('Done loop', nloop, 'at', time.ctime())
def main():
    print("starting at:", time.ctime())
    #ThreadFunc('loop').loop 跟一下两个式子相等
    #t = ThreadFunc('loop')
    #t.loop
    #以下t1, t2的定义方式相等
    t = ThreadFunc('loop')
    t1 = threading.Thread(target = t.loop, args = ('Loop1', 4))
    t2 = threading.Thread(target = ThreadFunc('loop').loop, args = ('Loop2', 2))

    t1.start()
    t2.start()

    t1.join()
    t2.join()

    print('all done at:', time.ctime())

if __name__ == '__main__':
    main()

threading的使用：
-直接利用threading.Thread生成Thread实例
1.t = threading.Thread(target = xxx, args = (xxx,))
2.t.start(): 启动多线程
3.t.join():等待多线程执行完成
守护线程：
-如果在程序中将子线程设置为守护线程，则子线程会在主线程结束的时候自动退出
-一般认为，守护线程不重要或者不允许离开主线程独立运行

线程常用属性：
-threading.currentThread: 返回当前线程变量
-threading.enumerate: 返回一个包含正在运行的线程的list，正在运行的线程指的是线程启动后，结束前的
-threading。activeCount：返回正在运行的线程数量，效果跟len(threading.enumerate)相同
-thr.setName: 给线程设置名字
-thr.getName：得到线程的名字

共享变量：当多个线程同时访问一个变量的时候，会产生共享变量的问题

import threading
sum = 0
loopSum = 100000
def myAdd():
    global sum, loopSum
    for i in range(1, loopSum):
        sum += 1
def myMinu():
    global sum, loopSum
    for i in range(1, loopSum):
        sum -= 1

if __name__ == '__main__':
    print('start.....{0}'.format(sum))
    t1 = threading.Thread(target = myAdd, args = ())
    t2 = threading.Thread(target = myMinu, args = ())
    t1.start()
    t2.start()
    t1.join()
    t2.join()

    print('done.....{0}'.format(sum))


锁：哪个资源需要多个线程，就锁谁

import threading
sum = 0
loopSum = 100000
lock = threading.Lock()
def myAdd():
    global sum, loopSum
    for i in range(1, loopSum):
        lock.acquire() #上锁
        sum += 1
        lock.release() #释放锁

def myMinu():
    global sum, loopsum
    for i in range(1, loopSum):
        lock.acquire()
        sum -= 1
        lock.release()

if __name__ == '__main__':
    print('starting.....{0}'.format(sum))
    t1 = threading.Thread(target = myAdd, args = ())
    t2 = threading.Thread(target = myMinu, args = ())
    t1.start()
    t2.start()

    t1.join()
    t2.join()

    print('done.....{0}'.format(sum))

锁：哪个资源需要多个线程，就锁谁

可重入锁：可以被一个线程多次申请