python 的 asyncio 中的可加入 PriorityQueue

Joinable PriorityQueue in python's asyncio

根据 documentation,队列有多种实现。我感兴趣的是 JoinableQueue 和 PriorityQueue,因为我想要一个具有优先级的可连接队列。

看来我只能获得低版本的其中一项功能。 IE。在 3.5 中,我可以区分 Queue(可连接)和 PriorityQueue,但在 3.5 以下的 python 中,有 JoinableQueue 和 PriorityQueue(参见下面的示例)。

是否可以将它们组合起来以获得在 3.4 中获得可连接 PriorityQueue 的通用方法?

try:
    # Python 3.4.
    from asyncio import JoinableQueue as Queue # joinable
    from asyncio import PriorityQueue          # I assume this one is not joinable
except ImportError:
    # Python 3.5.
    from asyncio import Queue                  # standard joinable
    from asyncio import PriorityQueue          # I assume this is the one I want

另一种方法可能会以某种方式影响 Queue?

由于 JoinableQueuePriorityQueue 的实现方式,只要您先列出 JoinableQueue,就可以通过多重继承对两者进行子类化来获得 JoinablePriorityQueue .

之所以可行,是因为 PriorityQueue 实现起来非常简单:

class PriorityQueue(Queue):
    """A subclass of Queue; retrieves entries in priority order (lowest first).

    Entries are typically tuples of the form: (priority number, data).
    """

    def _init(self, maxsize):
        self._queue = []

    def _put(self, item, heappush=heapq.heappush):
        heappush(self._queue, item)

    def _get(self, heappop=heapq.heappop):
        return heappop(self._queue)

虽然 JoinableQueue 更复杂,但它和 PriorityQueue 实现的唯一方法是 _put,而且至关重要的是,JoinableQUeue 在其调用 super()._put(..)拥有 put 实现,这意味着它将与 PriorityQueue 正确协作。

这是一个证明它有效的例子:

from asyncio import PriorityQueue, JoinableQueue
import asyncio
import random

class JoinablePriorityQueue(JoinableQueue, PriorityQueue):
    pass


@asyncio.coroutine
def consume(q):
    while True:
        a = yield from q.get()
        print("got a {}".format(a))
        if a[1] is None:
            q.task_done()
            return
        asyncio.sleep(1)
        q.task_done()

@asyncio.coroutine
def produce(q):
    for i in range(10):
        yield from q.put((random.randint(0,10), i))
    yield from q.put((100, None)) # Will be last
    asyncio.async(consume(q))
    print("waiting...")
    yield from q.join()
    print("waited")

loop = asyncio.get_event_loop()
q = JoinablePriorityQueue()
loop.run_until_complete(produce(q))

输出:

waiting...
got a (1, 2)
got a (2, 1)
got a (4, 4)
got a (5, 0)
got a (6, 8)
got a (6, 9)
got a (8, 3)
got a (9, 5)
got a (9, 7)
got a (10, 6)
got a (100, None)
waited