Method _add_reader

Lib/asyncio/selector_events.py:278–291

(self, fd, callback, *args)

                f'{transport!r}')

    def _add_reader(self, fd, callback, *args):
        self._check_closed()
        handle = events.Handle(callback, args, self, None)
        key = self._selector.get_map().get(fd)
        if key is None:
            self._selector.register(fd, selectors.EVENT_READ,
                                    (handle, None))
        else:
            mask, (reader, writer) = key.events, key.data
            self._selector.modify(fd, mask | selectors.EVENT_READ,
                                  (handle, writer))
            if reader is not None:
                reader.cancel()
        return handle

    def _remove_reader(self, fd):
        if self.is_closed():