Copied from https://github.com/python/asyncio/issues/484 """ From https://bugs.python.org/issue23242#msg284930 The following script is used to reproduce the bug: import asyncio async def execute(): process = await asyncio.create_subprocess_exec( "timeout", "0.1", "cat", "/dev/urandom", stdout=asyncio.subprocess.PIPE) while True: data = await process.stdout.read(65536) print('read %d bytes' % len(data)) if data: await asyncio.sleep(0.3) else: break asyncio.get_event_loop().run_until_complete(execute()) will produce following output and terminate with exception: read 65536 bytes read 65536 bytes Traceback (most recent call last): File "read_subprocess.py", line 18, in <module> asyncio.get_event_loop().run_until_complete(execute()) File "/usr/lib/python3.6/asyncio/base_events.py", line 466, in run_until_complete return future.result() File "read_subprocess.py", line 9, in execute data = await process.stdout.read(65536) File "/usr/lib/python3.6/asyncio/streams.py", line 634, in read self._maybe_resume_transport() File "/usr/lib/python3.6/asyncio/streams.py", line 402, in _maybe_resume_transport self._transport.resume_reading() File "/usr/lib/python3.6/asyncio/unix_events.py", line 401, in resume_reading self._loop._add_reader(self._fileno, self._read_ready) AttributeError: 'NoneType' object has no attribute '_add_reader' When the process exits https://github.com/python/asyncio/blob/master/asyncio/unix_events.py#L444 is called which sets this._loop = None Next time read() is called on the pipe the above exception is thrown. I have tried to fix this issue myself but would sometimes have read terminate too early and miss the last chunks of data. """ - BotoX

 New changeset f7f024a721d53978d03129e8eb5111d4f74534a9 by Yury Selivanov (Seth M. Larson) in branch '3.5': bpo-29704: Fix asyncio.SubprocessStreamProtocol closing (#405) https://github.com/python/cpython/commit/f7f024a721d53978d03129e8eb5111d4f74534a9 

 New changeset 604faba1db724951ee440337099d111e3ecade49 by Yury Selivanov (Seth M. Larson) in branch '3.6': bpo-29704: Fix asyncio.SubprocessStreamProtocol closing (#405) https://github.com/python/cpython/commit/604faba1db724951ee440337099d111e3ecade49 

 New changeset 481cb70a724687d12553d38a749c16034af68a1e by Yury Selivanov (Seth M. Larson) in branch 'master': bpo-29704: Fix asyncio.SubprocessStreamProtocol closing (#405) https://github.com/python/cpython/commit/481cb70a724687d12553d38a749c16034af68a1e