try: import usocket as socket, uselect as select, uerrno as errno except ImportError: try: import socket, select, errno select.poll # Raises AttributeError for CPython implementations without poll() except (ImportError, AttributeError): print("SKIP") raise SystemExit poller = select.poll() s = socket.socket() poller.register(s) # https://docs.python.org/3/library/select.html#select.poll.register # "Registering a file descriptor that’s already registered is not an error, # and has the same effect as registering the descriptor exactly once." poller.register(s) # 2 args are mandatory unlike register() try: poller.modify(s) except TypeError: print("modify:TypeError") poller.modify(s, select.POLLIN) poller.unregister(s) try: poller.modify(s, select.POLLIN) except OSError as e: assert e.errno == errno.ENOENT # poll after closing the socket, should return POLLNVAL poller.register(s) s.close() p = poller.poll(0) print(len(p), p[0][-1])