并发编程---死锁||递归锁---信号量---Event事件---定时器
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
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# 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 '''
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#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 '''
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
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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 '''
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
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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 '''
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()
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# 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 '''