New submission from Samuel Grayson <sam@samgrayson.me>: If all processes try to close the Queue immediately after someone has written to it, this causes [an error][1] (see the link for more details). Uncommenting any of the `time.sleep`s makes it work consistently again. import multiprocessing import time import logging import multiprocessing.util multiprocessing.util.log_to_stderr(level=logging.DEBUG) queue = multiprocessing.Queue(maxsize=10) def worker(queue): queue.put('abcdefghijklmnop') # "Indicate that no more data will be put on this queue by the # current process." --Documentation # time.sleep(0.01) queue.close() proc = multiprocessing.Process(target=worker, args=(queue,)) proc.start() # "Indicate that no more data will be put on this queue by the current # process." --Documentation # time.sleep(0.01) queue.close() proc.join() Perhaps this is because I am not understanding the documentation correctly, but in that case I would contend this is a documentation bug. Traceback (most recent call last): File "/usr/lib/python3.7/multiprocessing/queues.py", line 242, in _feed send_bytes(obj) File "/usr/lib/python3.7/multiprocessing/connection.py", line 200, in send_bytes self._send_bytes(m[offset:offset + size]) File "/usr/lib/python3.7/multiprocessing/connection.py", line 404, in _send_bytes self._send(header + buf) File "/usr/lib/python3.7/multiprocessing/connection.py", line 368, in _send n = write(self._handle, buf) BrokenPipeError: [Errno 32] Broken pipe [1]: https://stackoverflow.com/q/51680479/1078199 ---------- assignee: docs@python components: Documentation, Library (Lib) messages: 334490 nosy: charmonium, docs@python priority: normal severity: normal status: open title: Calling `Multiprocessing.Queue.close()` too quickly causes intermittent failure (BrokenPipeError) versions: Python 3.7 _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue35844> _______________________________________