python - yield协程demo

什么是协程，一个线程内的多个任务可以互相切换。由此得出我的理解：

• 任务可以暂停
• 任务暂停可以切换到其它任务
• 任务可以从暂停的地方重新执行

yield 就可以实现这样的操作

def coroutine_task1():
    print("coroutine_task1 started")
    x = yield
    print(f"coroutine_task1 received value: {x}")
    y = yield x * 2
    print(f"coroutine_task1 received value: {y}")
    yield y * 3

def coroutine_task2():
    print("coroutine_task2 started")
    x = yield
    print(f"coroutine_task2 received value: {x}")
    y = yield x * 2
    print(f"coroutine_task2 received value: {y}")
    yield y * 3


task1 = coroutine_task1()
task2 = coroutine_task2()

task1.send(None)
task2.send(None)

task1.send(10) 
task2.send(10)

task1.send(20) 
task2.send(20)

task1.close()
task2.close()

运行结果

coroutine_task1 started
coroutine_task2 started
coroutine_task1 received value: 10
coroutine_task2 received value: 10
coroutine_task1 received value: 20
coroutine_task2 received value: 20                               

 coroutine_task1 运行遇到yield就暂停了，切换到coroutine_task2进行执行了，2个task切换执行

由此引出yield遇到io操作，并且设置一个事件，io等待完成切换回来，在此io等待期间，可以切换到其它任务