并发编程---死锁||递归锁---信号量---Event事件---定时器

Posted 2020-11-01 Mr。yang

死锁

互斥锁：Lock()，互斥锁只能acquire一次

递归锁:  RLock()，可以连续acquire多次，每acquire一次计数器+1，只有计数为0时，才能被抢到acquire

# 死锁
from threading import Thread,Lock
import time

mutexA = Lock()
mutexB = Lock()

class MyThread(Thread):
    def run(self):
        self.f1()
        self.f2()

    def f1(self):
        mutexA.acquire()
        print(‘%s 拿到了A锁‘ %self.name)

        mutexB.acquire()
        print(‘%s 拿到了B锁‘ % self.name)
        mutexB.release()
        mutexA.release()

    def f2(self):
        mutexB.acquire()
        print(‘%s 拿到了B锁‘ % self.name)
        time.sleep(0.1)

        mutexA.acquire()
        print(‘%s 拿到了A锁‘ % self.name)
        mutexB.release()
        mutexA.release()

if __name__ == ‘__main__‘:
    for i in range(10):
        t=MyThread()
        t.start()
‘‘‘
打印结果:
Thread-1 拿到了A锁
Thread-1 拿到了B锁
Thread-1 拿到了B锁
Thread-2 拿到了A锁
‘‘‘

死锁

#互斥锁只能acquire一次
from threading import Thread,Lock
mutexA = Lock()
mutexA.acquire()
mutexA.release()

#递归锁:可以连续acquire多次，每acquier一次计数器就+1，只有计数为0时，才能被其他线程强到
from threading import Thread,RLock
import time

mutexB = mutexA = RLock()

class MyThread(Thread):
    def run(self):
        self.f1()
        self.f2()

    def f1(self):
        mutexA.acquire()
        print(‘%s 拿到了A锁‘ %self.name)

        mutexB.acquire()
        print(‘%s 拿到了B锁‘ % self.name)
        mutexB.release()
        mutexA.release()

    def f2(self):
        mutexB.acquire()
        print(‘%s 拿到了B锁‘ % self.name)
        time.sleep(2)

        mutexA.acquire()
        print(‘%s 拿到了A锁‘ % self.name)
        mutexB.release()
        mutexA.release()

if __name__ == ‘__main__‘:
    for i in range(10):
        t=MyThread()
        t.start()
‘‘‘
打印结果：
Thread-1 拿到了A锁
Thread-1 拿到了B锁
Thread-1 拿到了B锁
Thread-1 拿到了A锁
Thread-2 拿到了A锁
Thread-2 拿到了B锁
Thread-2 拿到了B锁
Thread-2 拿到了A锁
Thread-4 拿到了A锁
Thread-4 拿到了B锁
Thread-4 拿到了B锁
Thread-4 拿到了A锁
Thread-6 拿到了A锁
Thread-6 拿到了B锁
Thread-6 拿到了B锁
Thread-6 拿到了A锁
Thread-8 拿到了A锁
Thread-8 拿到了B锁
Thread-8 拿到了B锁
Thread-8 拿到了A锁
Thread-10 拿到了A锁
Thread-10 拿到了B锁
Thread-10 拿到了B锁
Thread-10 拿到了A锁
Thread-5 拿到了A锁
Thread-5 拿到了B锁
Thread-5 拿到了B锁
Thread-5 拿到了A锁
Thread-9 拿到了A锁
Thread-9 拿到了B锁
Thread-9 拿到了B锁
Thread-9 拿到了A锁
Thread-7 拿到了A锁
Thread-7 拿到了B锁
Thread-7 拿到了B锁
Thread-7 拿到了A锁
Thread-3 拿到了A锁
Thread-3 拿到了B锁
Thread-3 拿到了B锁
Thread-3 拿到了A锁
‘‘‘

递归锁

信号量

信号量也是一把锁，可以指定信号量为5，对比互斥锁同一时间只能有一个任务抢到锁去执行

信号量同一时间可以有5个任务拿到锁去执行

信号量：同一时间有多个线程在进行

from threading import Thread,Semaphore,currentThread
import time,random

sm=Semaphore(3) #厕所的坑

def task():
    # sm.acquire()
    # print(‘%s in‘ %currentThread.getName())
    # sm.release()
    with sm:
        print(‘%s in‘ %currentThread().getName())
        time.sleep(random.randint(2,3))

if __name__ == ‘__main__‘:
    for i in range(10):
        t=Thread(target=task)
        t.start()
‘‘‘
打印结果：
Thread-1 in
Thread-2 in
Thread-3 in

Thread-4 in

Thread-5 in
Thread-6 in

Thread-7 in

Thread-9 in
Thread-8 in
Thread-10 in
‘‘‘

信号量

Event事件

event.isSet(): 返回event的状态值
event.wait()：如果 event.isSet()==False将阻塞线程
event.set()：  设置event的状态值为True，所有阻塞池的线程激活进入就绪状态,等待操作系统调度
event.clear():  恢复event的状态值为False

from threading import Thread,Event
import time

event = Event()
# event.wait() 在原地等,指导执行到event.set()
# event.set() 等待结束

def student(name):
    print(‘学生%s 正在听课‘ %name)
    event.wait(2)
    print(‘学生%s 课间活动‘ %name)

def teacher(name):
    print(‘老师%s 正在授课‘ %name)
    time.sleep(5)
    event.set()

if __name__ == ‘__main__‘:
    stu1 = Thread(target=student,args=(‘alex‘,))
    stu2 = Thread(target=student,args=(‘yang‘,))
    stu3 = Thread(target=student,args=(‘hang‘,))
    tea1 = Thread(target=teacher,args=(‘ding‘,))

    stu1.start()
    stu2.start()
    stu3.start()
    tea1.start()
‘‘‘
打印结果：
学生alex 正在听课
学生yang 正在听课
学生hang 正在听课
老师ding 正在授课
学生hang 课间活动
学生yang 课间活动
学生alex 课间活动
‘‘‘


#设置连接的超时时间
from threading import Thread,Event,currentThread
import time

event = Event()

def conn():
    n=0
    while not event.is_set():
        if n == 3:
            print(‘%s try too many‘ %currentThread().getName())
            return
        print(‘%s try %s‘ %(currentThread().getName(),n))
        event.wait(0.5)
        n+=1


    print(‘%s is connecting‘ %currentThread().getName())

def check():
    print(‘%s is checking‘ %currentThread().getName())
    time.sleep(5)
    event.set()

if __name__ == ‘__main__‘:
    for i in range(3):
        t=Thread(target=conn)
        t.start()
    t=Thread(target=check)
    t.start()
‘‘‘
打印结果：
Thread-1 try 0
Thread-2 try 0
Thread-3 try 0
Thread-4 is checking
Thread-1 try 1
Thread-3 try 1
Thread-2 try 1
Thread-1 try 2
Thread-3 try 2
Thread-2 try 2
Thread-1 try too many
Thread-3 try too many
Thread-2 try too many
‘‘‘

Event

定时器

定时器：隔一段时间，执行一个任务,每启动一个定时器，就等于启动一个线程

t=Timer(5,task,args=(‘egon‘,))

t.start()

t.cancel()

# from  threading import Timer
#
# def task(name):
#     print(‘hello %s‘ %name)
#
# t=Timer(5,task,args=(‘egon‘,))
# t.start()

#验证码
from threading import Timer
import random

class Code:
    def __init__(self):
        self.make_cache()

    def make_cache(self,interval=60):
        self.cache = self.make_code()
        print(self.cache)
        self.t = Timer(interval,self.make_cache)
        self.t.start()

    def make_code(self,n=4):
        res=‘‘
        for i in range(n):
            s1 = str(random.randint(0,9))
            s2 = chr(random.randint(65,90))
            res+=random.choice([s1,s2])
        return res

    def check(self):
        while True:
            code = input(‘输入你的验证码>>: ‘).strip()
            if code.upper() == self.cache:
                print(‘验证码输入正确‘)
                self.t.cancel()
                break

obj=Code()
obj.check()

‘‘‘
打印结果:
X095
输入你的验证码>>: X095
验证码输入正确
‘‘‘

定时器