如何在Django中创建对象队列?

时间:2009-11-03 02:53:33

标签: python django django-models queue

我是 Django 的新手,我正在尝试自己构建一个博客。我正在尝试使用nodequeue模块创建一个我在 Drupal 中实现的功能。

我想要做的是能够创建对象队列,例如博客文章队列。下面,我将描述我如何想象队列的工作原理:

  • 每个队列的大小应由用户定义。
  • 应记录将对象添加到队列的日期。
  • 我希望能够定义属于每个队列的项目的顺序(但我认为这将非常困难)。
  • 如果队列已满,则添加额外项目应丢弃队列中最旧的项目。

此功能如何有用的一个示例是创建精选帖子队列。

我目前的知识不允许我弄清楚什么是正确的方法。我会很感激任何指针。

提前致谢

3 个答案:

答案 0 :(得分:5)

这是一种方法:

import collections, datetime, itertools

class nodequeue(object):
  def __init__(self, N):
    self.data = collections.deque(N * [(None, None)])
  def add(self, anobj):
    self.data.popleft()
    self.data.push((anobj, datetime.datetime.now())
  def __iter__(self):
    it = iter(self.data)
    return it.dropwhile(lambda x: x[1] is None, self.data)

这忽略了“排序”的需求,但这不会太难添加,例如:

class nodequeueprio(object):
  def __init__(self, N):
    self.data = collections.deque(N * [(None, None, None)])
  def add(self, anobj, prio):
    self.data.popleft()
    self.data.push((anobj, datetime.datetime.now(), prio)
  def __iter__(self):
    it = iter(self.data)
    return sorted(it.dropwhile(lambda x: x[1] is None, self.data),
                  key=operator.itemgetter(2))

我认为使用占位符None预填充队列会简化代码,因为add总是可以在添加新东西之前删除最左边(最旧或无)的项目 - 即使{{1}然后必须删除占位符,这不是太糟糕。

答案 1 :(得分:3)

亚历克斯的方法很棒。我不会假装与他的专业水平竞争,但为了完整起见,这是使用梦幻般的Queue.Queue课程的另一种方法(奖励:线程安全,但根据你的描述,这对你有点无用) 。这对您来说可能更容易理解,因为您对此表示了一些担忧:

myqueue.py

#!/usr/bin/python

# Renamed in Python 3.0
try: from Queue import Queue, Full, Empty
except: from queue import Queue, Full, Empty
from datetime import datetime

# Spec 1: Size of each queue should be user-defined.
#   - maxsize on __init__

# Spec 2: Date an object is added should be recorded.
#   - datetime.now() is first member of tuple, data is second

# Spec 3: I would like to be able to define the order of the items that
# belong to each queue.
#   - Order cannot be rearranged with this queue.

# Spec 4: If the queue is full, the addition of an extra item should discard
# the oldest item of the queue.
#   - implemented in put()

class MyQueue(Queue):
    "Wrapper around Queue that discards old items instead of blocking."
    def __init__(self, maxsize=10):
        assert type(maxsize) is int, "maxsize should be an integer"
        Queue.__init__(self, maxsize)

    def put(self, item):
        "Put an item into the queue, possibly discarding an old item."
        try:
            Queue.put(self, (datetime.now(), item), False)
        except Full:
            # If we're full, pop an item off and add on the end.
            Queue.get(self, False)
            Queue.put(self, (datetime.now(), item), False)

    def put_nowait(self, item):
        "Put an item into the queue, possibly discarding an old item."
        self.put(item)

    def get(self):
        "Get a tuple containing an item and the datetime it was entered."
        try:
            return Queue.get(self, False)
        except Empty:
            return None

    def get_nowait(self):
        "Get a tuple containing an item and the datetime it was entered."
        return self.get()


def main():
    "Simple test method, showing at least spec #4 working."
    queue = MyQueue(5)
    for i in range(1, 7):
        queue.put("Test item number %u" % i)

    while not queue.empty():
        time_and_data = queue.get()
        print "%s => %s" % time_and_data


if __name__ == "__main__":
    main()

预期产出

2009-11-02 23:18:37.518586 => Test item number 2
2009-11-02 23:18:37.518600 => Test item number 3
2009-11-02 23:18:37.518612 => Test item number 4
2009-11-02 23:18:37.518625 => Test item number 5
2009-11-02 23:18:37.518655 => Test item number 6

答案 2 :(得分:0)

您可以使用django-activity-stream。它没有Nodequeue所具有的UI,但它可以用于创建对象的不同队列。