python之互斥锁

• 互斥锁

from threading import Thread,Lock
import os,time

#互斥锁
def work():
    global n
    lock.acquire() # 锁住n,让他依次执行
    temp = n
    print(n)
    time.sleep(0.1)
    n=temp-1
    print(n)
    lock.release() #释放锁

if __name__ == '__main__':
    lock=Lock()
    n = 100
    l = []
    for i in range(100):
        p=Thread(target=work)
        l.append(p)
        p.start()
    for p in l:
        p.join()

• 递归锁

import threading
import time

# 递归锁
#RLcok类的用法和Lock类一模一样，但它支持嵌套，在多个锁没有释放的时候一般会使用RLcok类。
def Fun(lock):
    global gl_num
    lock.acquire()
    gl_num += 1
    time.sleep(1)
    print(gl_num)
    lock.release()

if __name__ == '__main__':
    gl_num = 0
    lock = threading.RLock()
    for i in range(10):
        t = threading.Thread(target=Fun,args=(lock,))
        t.start()

• 信号量(BoundedSenaohore类)

import threading
import time

#信号量(BoundedSenaohore类)

def run(n, semaphore):
    semaphore.acquire() #加锁
    time.sleep(1)
    print("run the thread:%s
" %n)
    semaphore.release() #释放锁

if __name__ == '__main__':
    num = 0
    semaphore = threading.BoundedSemaphore(5) #最多允许5个线程同时运行
    for i in range(22):
        #print(i)
        t = threading.Thread(target=run,args=("t-%s" % i, semaphore))
        t.start()
    while threading.active_count() !=1:
        print("while",threading.active_count())
    else:
        print('-----all threads done----')

• 事件(Event类)

import threading
import time

"""
事件（Event类）
python线程的事件用于主线程控制其他线程的执行，事件是一个简单的线程同步对象，其主要提供以下几个方法：

clear 将flag设置为“False”
set 将flag设置为“True”
is_set 判断是否设置了flag
wait 会一直监听flag，如果没有检测到flag就一直处于阻塞状态
事件处理的机制：全局定义了一个“Flag”，当flag值为“False”，那么event.wait()就会阻塞，当flag值为“True”，那么event.wait()便不再阻塞。
"""

#利用Event类模拟红绿灯

event = threading.Event()

def lighter():
    count = 0
    event.set() #初始值为绿灯
    while True:
        if 5 < count <= 10:
            event.clear() #红灯，清除标志位
            print("33[41;1mred light is on..33[0m")
        elif count > 10:
            event.set() #
            count = 0
        else:
            print("33[42;1mgreen light is on...33[0m")

        time.sleep(1)
        count += 1

def car(name):
    while True:
        if event.is_set(): #判断是否设置了标志位
            print("[%s] running..."%name)
            time.sleep(1)
        else:
            print("[%s] sees red light,waiting...."%name)
            event.wait()
            print("[%s] green light is on,start going... "%name)


light = threading.Thread(target=lighter)
light.start()


car = threading.Thread(target=car,args=("MINI",))
car.start()