[Python-ideas] Queue suggestions

[George Sakkis]

I'd like to propose a signature simplification and a new method for
the Queue.Queue class:

1) Drop the optional `block` argument from put() and get(), since all
the meaningful combinations of  (block, timeout) are equivalent to
passing block = (timeout is None or timeout>0). IOW, instead of
passing block=False pass timeout=0 (or negative). Obviously this is to
be considered for 3.x only.

2) Add a new `rotate` method as the atomic equivalent of
put_nowait(get_nowait()). Currently I use the following subclass but
it would be nice to have it in the base Queue:

class RQueue(Queue):

    def rotate(self, n=1):
        '''Rotate this queue n steps to the left (if it is not empty).

        Rotating one step is equivalent to an atomic
q.put_nowait(q.get_nowait()).
        '''
        if n < 0:
            raise ValueError('n must be non-negative')
        self.mutex.acquire()
        try:
            if not self._empty():
                self._rotate(n)
        finally:
            self.mutex.release()

    def __init__(self, maxsize=0):
        Queue.__init__(self, maxsize)
        if hasattr(self.queue, 'rotate'):  # deque has rotate() since v2.5
            def _rotate(n):
                # negative n for left rotate
                self.queue.rotate(-n)
        else:
            def _rotate(n):
                put,get = self._put, self._get
                for i in xrange(n):
                    put(get())
        self._rotate = _rotate


What do you think ?

George