在python里协程使用同步锁Lock的实例_Python

在python里协程使用同步锁Lock的实例

2021-05-30 00:21caimouse Python

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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