[Python-ideas] Add closing and iteration to threading.Queue
python at mrabarnett.plus.com
Sun Oct 21 19:48:14 EDT 2018
On 2018-10-21 22:30, Antoine Pitrou wrote:
> On Sun, 21 Oct 2018 19:58:05 +0200
> Vladimir Filipović <hemflit at gmail.com>
>> To anticipate a couple more possible questions:
>> - What would this proposal do about multiple producers/consumers
>> needing to jointly decide _when_ to close the queue?
>> Explicitly nothing.
>> The queue's state is either closed or not, and it doesn't care who
>> closed it. It needs to interact correctly with multiple consumers and
>> multiple producers, but once any one piece of code closes it, the
>> correct interaction is acting like a closed queue for everybody.
> Ah. This is the one statement that makes me favorable to this idea.
> When there is a single consumer, it's easy enough to send a sentinel.
> But when there are multiple consumers, suddenly you must send exactly
> the right number of sentinels (which means you also have to careful
> keep track of their number, which isn't always easy). There's some
> delicate code doing exactly that in concurrent.futures.
You don't need more than one sentinel. When a consumer sees the
sentinel, it just needs to put it back for the other consumers.
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