Chris Angelico <[email protected]>:
> On Mon, Feb 22, 2016 at 1:15 AM, Ho Yeung Lee <[email protected]>
> wrote:
>> 0 ---> 2 --> 3--> 1 ---> 0
>> ---> 4 /
>
> So after task 2 completes, tasks 3 and 4 both become available (and
> can run in parallel), but then task 1 must wait until both have
> finished before it runs? I'm not an asyncio expert, but this sounds
> like a fairly straight-forward dependency requirement. If you were to
> implement these as four separate threads, you would have threads 3 and
> 4 raise semaphores which thread 1 blocks on; I'm sure there'll be an
> equivalent in asyncio.
>
> [...]
>
> (Can an asyncio expert tell me how to tidy this code up, please? I'm
> sure this isn't the cleanest.)
Not an expert, but this does the trick:
========================================================================
#!/usr/bin/env python3
import asyncio
def main():
loop = asyncio.get_event_loop()
loop.run_until_complete(t0())
async def t0():
print("start t0")
await t2()
await asyncio.wait([ t3(), t4() ])
await t1()
print("finish t0")
async def t1():
print("start t1")
await asyncio.sleep(1)
print("finish t1")
async def t2():
print("start t2")
await asyncio.sleep(1)
print("finish t2")
async def t3():
print("start t3")
await asyncio.sleep(1)
print("finish t3")
async def t4():
print("start t4")
await asyncio.sleep(1)
print("finish t4")
if __name__ == '__main__':
main()
========================================================================
Marko
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