Filed a bug as requested at http://bugs.python.org/issue24837. Victor, I am
running linux (redhat 6).
If this is indeed a bug that will be fixed, i was wondering if the
following will also be supported.
-------------------------------------------------------------------------------------
import asyncio
async def sleepWithShell(loop=None):
process = await asyncio.create_subprocess_shell("sleep 2", loop=loop)
await process.wait()
return True
def sleepWithNewLoop():
"""This function uses asyncio in its implementation, but wants the fact
that it uses asyncio to be opaque to the user.
i.e, it needs to work both when the user isn't using asyncio at all,
and when the user already has his own loop and is calling this function
from a
coroutine in his loop. Is that supported by asyncio?
"""
loop = asyncio.new_event_loop()
result = loop.run_until_complete(sleepWithShell(loop))
loop.close()
return result
async def sleepWithMainLoopAndNewLoop():
result = await sleepWithShell()
print("sleep with shell in main loop ", result)
result = sleepWithNewLoop()
print("sleep with shell in new 'nested' loop ", result)
return result
def main():
asyncio.get_event_loop().run_until_complete(sleepWithMainLoopAndNewLoop())
asyncio.get_event_loop().close()
if __name__ == "__main__":
main()
-------------------------------------------------------------------------------------
sleepWithNewLoop is a poor example, but there's a lot of functions in a
library that I maintain that could run faster if i could use asyncio in the
implementation. I want the functions to work without having to require the
user to manage an event loop, but I also want them to not affect the user's
existing loop if he already has one.
Thanks for your time,
Chetan
On Sunday, August 9, 2015 at 2:51:32 PM UTC-4, Guido van Rossum wrote:
>
> Wait, why isn't that just a bug that wait() doesn't know the associated
> loop?
>
> It seems the child watcher is only associated with the loop on
> set_event_loop(), which in your example doesn't get called (and it
> shouldn't need to be called).
>
> I've reproduced your bug; please file a bug per Victor's instructions.
>
> --Guido
>
> On Sun, Aug 9, 2015 at 5:00 PM, <cheta...@gmail.com <javascript:>> wrote:
>
>> Hello,
>>
>> I tried to run the following program with Python-3.5.0b4, and it hangs
>> forever:
>>
>> --------------------------------------------
>> import asyncio
>>
>> async def sleepWithShell(loop):
>> process = await asyncio.create_subprocess_shell("sleep 2", loop=loop)
>> await process.wait()
>> return True
>>
>> async def sleepWithAsyncio(loop):
>> await asyncio.sleep(2, loop=loop)
>> return True
>>
>> def main():
>> loop = asyncio.new_event_loop()
>> coros = [ sleepWithShell(loop) for i in range(5)]
>> results = loop.run_until_complete(asyncio.gather(*coros, loop=loop))
>> loop.close()
>> print(results)
>>
>> if __name__ == "__main__":
>> main()
>> ----------------------------------------------
>>
>> In main, if you replace sleepWithShell with sleepWithAsyncio the program
>> will run as expected. I looked through the code, and I now understand that
>> process.wait doesn't work because the child process watcher is not
>> associated with the loop that's passed.
>>
>> In an ideal world, i'd like to be able to create a loop, use it and close
>> it without changing any global state. It seems like that's possible with
>> some coroutines, but not with create_subprocess_shell.
>>
>> If passing a custom loop to create_subprocess_shell isn't always
>> supported, I was wondering if it's possible to check and raise an
>> exception in subprocess.Process.wait instead of just hanging forever.
>>
>> Thanks,
>> Chetan
>>
>>
>
>
> --
> --Guido van Rossum (python.org/~guido)
>
