我注意到我不能使用PriorityQueue for Objects？

Question

我有一个ADT(PCB又名过程控制块),我想将它们放入优先级队列.我该怎么做？

我已经使用了如何将项目放入优先级队列？具有次要优先级以确保队列的正确排序.在这里我可以使PCB具有可比性,但在另一个类中,它可能没有意义吗？在那种情况下我可以做什么？

UPDATE

我的代码非常类似于发布的/sf/answers/650283231/

class PCB:
    ...

# in my class extending `PriorityQueue`
PriorityQueue.put(self, (priority, self.counter, pcb))

我认为问题是pcb在这里仍然没有可比性

Answer 1

好的只是关闭这个问题.继承人我做了什么:

使ADT具有可比性:实施__lt__().

def __lt__(self, other):
    selfPriority = (self.priority, self.pid)
    otherPriority = (other.priority, other.pid)
    return selfPriority < otherPriority

这样,我可以简单地使用 queue.put(obj)

我发现@larsmans说得对

" 如果优先级和计数器始终具有可比性,并且没有两个计数器具有相同的值,则整个三元组具有可比性 "

jiewmeng@JM:~$ python3.2
Python 3.2.2 (default, Sep  5 2011, 21:17:14) 
[GCC 4.6.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> class Test:
...     def __init__(self, name):
...             self.name = name
... 
>>> from queue import PriorityQueue
>>> q = PriorityQueue()

# duplicate priorities triggering unorderable error
>>> q.put((2, Test("test1")))
>>> q.put((1, Test("test1")))
>>> q.put((3, Test("test1")))
>>> q.put((3, Test("test1")))
>>> q.put((3, Test("test2")))
>>> while not q.empty():
...     print(q.get().name)
... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "/usr/lib/python3.2/queue.py", line 195, in get
    item = self._get()
  File "/usr/lib/python3.2/queue.py", line 245, in _get
    return heappop(self.queue)
TypeError: unorderable types: Test() < Test()

# unique priority fields thus avoiding the problem
>>> q = PriorityQueue()
>>> q.put((3, Test("test1")))
>>> q.put((5, Test("test5")))

>>> while not q.empty():
...     print(q.get()[1].name)
... 
test1
test5