在python里协程使用同步锁Lock的实例
尽管asyncio库是使用单线程来实现协程的,但是它还是并发的,乱序执行的。可以说是单线程的调度系统,并且由于执行时有延时或者I/O中断等因素,每个协程如果同步时,还是得使用一些同步对象来实现。
比如asyncio就定义了一个锁对象Lock,它一次只允许一个协程来访问共享的资源,如果多协程想访问就会阻塞起来,也就是说如果一个协程没有释放这个锁,别的协程是没有办法访问共享的资源。
例子:
importasyncio importfunctools defunlock(lock): print('callbackreleasinglock') lock.release() asyncdefcoro1(lock): print('coro1waitingforthelock') withawaitlock: print('coro1acquiredlock') print('coro1releasedlock') asyncdefcoro2(lock): print('coro2waitingforthelock') awaitlock try: print('coro2acquiredlock') finally: print('coro2releasedlock') lock.release() asyncdefmain(loop): #Createandacquireasharedlock. lock=asyncio.Lock() print('acquiringthelockbeforestartingcoroutines') awaitlock.acquire() print('lockacquired:{}'.format(lock.locked())) #Scheduleacallbacktounlockthelock. loop.call_later(0.1,functools.partial(unlock,lock)) #Runthecoroutinesthatwanttousethelock. print('waitingforcoroutines') awaitasyncio.wait([coro1(lock),coro2(lock)]), event_loop=asyncio.get_event_loop() try: event_loop.run_until_complete(main(event_loop)) finally: event_loop.close()
输出结果如下:
acquiringthelockbeforestartingcoroutines lockacquired:True waitingforcoroutines coro1waitingforthelock coro2waitingforthelock callbackreleasinglock coro1acquiredlock coro1releasedlock coro2acquiredlock coro2releasedlock
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