方法2是错误的,因为你在两个步骤中开展行动时,可以开展行动。 在方法2中,你检查点是否空了,然后(很快,但仍在以后)试图拿到该项目。 你们有两条read子把物品从胎盘中拿走? 空洞的陷阱仍然可能失败。 在检查后,如果在问询中添加一个物品,那是空的? 这些是各种机会之窗,这些机会之窗按照并行的法典 cr。

无论采取哪一步,它迄今为止都是更好的选择。

import Queue

q = Queue.Queue()

try:
    task = q.get(False)
except Queue.Empty:
    # Handle empty queue here
    pass
else:
    # Handle task here and call q.task_done()

“例外应当是错误”。 例外只是另一种通信渠道,使用它们。 此处使用“e”条款来缩小例外条款的范围。

如果是多读/多处理法(这是使用任何途径的良好理由),那么肯定的方法1。 在<条码>q.empty() 电话和q.get( 电话之间,心脏的杰克本可能偷走了你的条条arts!

一种论点是,方法1是错误的,因为空洞并非错误,因此不应使用Quue处理。 就业例外

一种例外不一定是“承运人”,它是一个一般的流动控制机制,在少数情况下(SysExit、制止渗透等)的确如此使用。

The good question here is: what will be the most common case - empty or non-empty queue. Unless you know for sure, you want to AskBeforeYouLeap, cause it s very probably way cheaper.

面对同一问题,不寻找Queue模块;我知道这大约一年后,但未来的读者可能会发现以下示范例子:

from queue import Queue, Full, Empty
q = Queue(maxsize=3)    # finite queue, maxsize <= 0 -> infinite queue

# enqueue a couple of items
q.put( a )
q.put( b )

# trying to dequeue excessively
for _ in range(4):
    try:
        print(f dequeued: {q.get(block=False)} )

    except Empty:
        print( empty queue! )

# trying to enqueue excessively
for ch in [ a ,  b ,  c ,  d ]:
    try:
        print(f enqueueing : {ch} -> , end=   )
        q.put(ch, block=False)
        print( success :) )

    except Full:
        print( full queue :( )

and here is the sample output:

dequeued: a
dequeued: b
empty queue!
empty queue!
enqueueing : a -> success :)
enqueueing : b -> success :)
enqueueing : c -> success :)
enqueueing : d -> full queue :(

Please note, by default, get() and put() are both blocking methods (block=True) and will block the process until a new item is inserted into the queue (get), or an item is consumed to allow room for a new item (put). See here for more details.

在某些法典中,我刚才写道,我需要迅速空洞,只处理最后一个项目,我认为这是最近的事件,也是我所关心的。

我基本上利用你的方法1来这样做。

# pop data from queue until it is empty and so have the most recent data:
data = self.queue.get()    # first call to the queue blocks, so when get past this line, data should be valid
try:
    while True:
        data = self.queue.get_nowait()    # subsequent calls do NOT block; overwrite data with the last valid result; this call will raise an Empty Exception after have read all data from the queue
except Empty:
    pass

如果我能正确理解斯堪的斯温特,这是我空洞的唯一好办法。

尽管如此,我还是怀着仇恨,叫APIC!

Sorry Pythonistas, its defective. There ought to be a nonblocking way that I can poll the queue for its first item and it returns None if it is empty instead of raising an Empty. Using an Exception here is a terrible choice not only because it requires an awkward try/except but also because it is awful for performance: stacktraces are expensive to generate. The code above is in a real critical section for me.

参看:Java s Queue界面污染方法;另见this问题SO。 极佳的APIC设计。