python里协程使用同步锁Lock 在python里协程使用同步锁Lock的实例
caimouse 人气:0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:
import asyncio import functools def unlock(lock): print('callback releasing lock') lock.release() async def coro1(lock): print('coro1 waiting for the lock') with await lock: print('coro1 acquired lock') print('coro1 released lock') async def coro2(lock): print('coro2 waiting for the lock') await lock try: print('coro2 acquired lock') finally: print('coro2 released lock') lock.release() async def main(loop): # Create and acquire a shared lock. lock = asyncio.Lock() print('acquiring the lock before starting coroutines') await lock.acquire() print('lock acquired: {}'.format(lock.locked())) # Schedule a callback to unlock the lock. loop.call_later(0.1, functools.partial(unlock, lock)) # Run the coroutines that want to use the lock. print('waiting for coroutines') await asyncio.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:
acquiring the lock before starting coroutines lock acquired: True waiting for coroutines coro1 waiting for the lock coro2 waiting for the lock callback releasing lock coro1 acquired lock coro1 released lock coro2 acquired lock coro2 released lock
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