threadpooltest.py

import threading

from asyncio_extras.threads import threadpool


async def main():
    print('main:', threading.current_thread())

    for _ in range(4):
        async with threadpool():
            import time
            print('within threadpool:', threading.current_thread())
            time.sleep(1)
            print('within threadpool:', threading.current_thread(), 'done')

    print('main:', threading.current_thread(), 'done')


if __name__ == '__main__':
    import asyncio
    loop = asyncio.get_event_loop()
    #loop.run_until_complete(main())
    loop.run_until_complete(asyncio.wait([main(), main()]))

$ python threadpooltest.py
main: <_MainThread(MainThread, started 139720800528128)>
main: <_MainThread(MainThread, started 139720800528128)>
within threadpool: <Thread(Thread-1, started daemon 139720720750336)>
within threadpool: <Thread(Thread-1, started daemon 139720720750336)> done
within threadpool: <Thread(Thread-2, started daemon 139720712357632)>
within threadpool: <Thread(Thread-2, started daemon 139720712357632)> done
within threadpool: <Thread(Thread-1, started daemon 139720720750336)>
within threadpool: <Thread(Thread-1, started daemon 139720720750336)> done
within threadpool: <Thread(Thread-5, started daemon 139720687179520)>
within threadpool: <Thread(Thread-5, started daemon 139720687179520)> done
main: <_MainThread(MainThread, started 139720800528128)> done
Task exception was never retrieved
future: <Task finished coro=<main() done, defined at threadpooltest.py:6> exception=ValueError('coroutine already executing',)>
Traceback (most recent call last):
  File "/usr/x86_64-pc-linux-gnu/lib/python3.5/asyncio/tasks.py", line 241, in _step
    result = coro.throw(exc)
  File "threadpooltest.py", line 10, in main
    async with threadpool():
  File "/home/nakamuray/virtualenvs/sandbox35/lib/python3.5/site-packages/asyncio_extras/threads.py", line 46, in __await__
    yield future
  File "/usr/x86_64-pc-linux-gnu/lib/python3.5/asyncio/tasks.py", line 290, in _wakeup
    future.result()
  File "/usr/x86_64-pc-linux-gnu/lib/python3.5/asyncio/futures.py", line 274, in result
    raise self._exception
  File "/usr/x86_64-pc-linux-gnu/lib/python3.5/concurrent/futures/thread.py", line 55, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/home/nakamuray/virtualenvs/sandbox35/lib/python3.5/site-packages/asyncio_extras/threads.py", line 28, in exec_when_ready
    coro.send(None)
ValueError: coroutine already executing