# Async examples.  Per the book, cop/ypaste, stub out with """, or run as a whole.



import time, asyncio
def now(): 
    return time.strftime('[%H:%M:%S]')      # Local time, as hour:minute:second



print('1-----------------------------------------------------')



def producer(label):
    time.sleep(2)                              # Pause for two seconds: blocking
    return f'All done, {label}, {now()}'       # And return a result

def main():
    print('Start =>', now())
    print(producer(f'serial task 1'))          # Run three steps in sequence
    print(producer(f'serial task 2'))          # Waiting for each one to finish
    print(producer(f'serial task 3'))          # Before doing anything else
    print('Stop  =>', now())

main()



print('2-----------------------------------------------------')



async def producer(label):                     # await requires async
    await asyncio.sleep(2)                     # Call nonblocking/awaitable sleep
    return f'All done, {label}, {now()}'       # Result of await expression

async def main():
    print('Start =>', now())
    task1 = asyncio.create_task(producer(f'async task 1'))
    task2 = asyncio.create_task(producer(f'async task 2'))
    task3 = asyncio.create_task(producer(f'async task 3'))
    print(await task1) 
    print(await task2) 
    print(await task3)                         # Wait for tasks to finish
    print('Stop  =>', now())

asyncio.run(main())                            # Start event-loop schedule



print('3-----------------------------------------------------')



async def producer(label):
    await asyncio.sleep(2)
    return f'All done, {label}, {now()}'

async def main():
    print('Start =>', now())
    tasks = []
    for i in range(3):
        tasks.append(asyncio.create_task(producer(f'async task {i+1}')))
    for task in tasks:
        print(await task)
    print('Stop  at', now())

asyncio.run(main())



print('4-----------------------------------------------------')



async def producer(label):
    await asyncio.sleep(2)
    return f'All done, {label}, {now()}'

async def main():
    print('Start =>', now())
    coros = [producer(f'async task {i+1}') for i in range(3)]
    for nextdone in asyncio.as_completed(coros):
        print(await nextdone)
    print('Stop  at', now())

asyncio.run(main())



print('5-----------------------------------------------------')



async def producer(label):
    await asyncio.sleep(2)
    return f'All done, {label}, {now()}'

async def main():
    print('Start =>', now())
    coro1 = producer(f'async task 1')
    coro2 = producer(f'async task 2')
    coro3 = producer(f'async task 3')
    results = await asyncio.gather(coro1, coro2, coro3)
    print(results) 
    print('Stop  at', now())

asyncio.run(main())



print('6-----------------------------------------------------')



async def producer(label):
    await asyncio.sleep(2)
    return f'All done, {label}, {now()}'

async def main():
    print('Start =>', now())
    print(await asyncio.gather(*[producer(f'async task {i+1}') for i in range(3)]))
    print('Stop  at', now())

asyncio.run(main())



print('7-----------------------------------------------------')



async def producer(label):
    await asyncio.sleep(2)
    return f'All done, {label}, {now()}'

async def main():
    print('Start =>', now())
    async with asyncio.TaskGroup() as tg:
        tasks = [tg.create_task(producer(f'async task {i+1}')) for i in range(3)]
    for task in tasks:
        print(task.result())
    print('Stop  at', now())

asyncio.run(main())



print('8-----------------------------------------------------')



async def producer(label):
    for i in range(3):
        await asyncio.sleep(2)
        yield f'All done, {label} {i+1}, {now()}'

async def main():
    print('Start =>', now())
    async for reply in producer('async task'):
        print(reply)
    print('Stop  at', now())

asyncio.run(main())