如何将元素放在 Python 队列的底部

Question

我有一个由不同线程填充的队列。我有一个线程，我从队列中获取项目并将它们发送到另一个目的地。当最后一个操作失败时，我想再次将元素放入队列中，但放在队列底部，因为我希望出列线程将它们作为第一优先级出列。有没有办法做到这一点？也许使用其他 class 而不是 Queue.queue?

Answer 1

deque怎么样？

Deques support thread-safe, memory efficient appends and pops from either side of the deque with approximately the same O(1) performance in either direction.

Answer 2

这是一个实现——它基本上是 Queue.put method 和 self._put(item) 替换为 self.queue.appendleft(item)

from Queue import Queue

class MyQueue(Queue):
    def putleft(self, item, block=True, timeout=None):
        self.not_full.acquire()
        try:
            if self.maxsize > 0:
                if not block:
                    if self._qsize() == self.maxsize:
                        raise Full
                elif timeout is None:
                    while self._qsize() == self.maxsize:
                        self.not_full.wait()
                elif timeout < 0:
                    raise ValueError("'timeout' must be a non-negative number")
                else:
                    endtime = _time() + timeout
                    while self._qsize() == self.maxsize:
                        remaining = endtime - _time()
                        if remaining <= 0.0:
                            raise Full
                        self.not_full.wait(remaining)
            self.queue.appendleft(item)
            self.unfinished_tasks += 1
            self.not_empty.notify()
        finally:
            self.not_full.release()

如何将元素放在 Python 队列的底部

How to put elements on bottom of Python queue

python

queue

multithreading