Queue peek?
in [Python]
|
From: Floris Bruynooghe on 3 Mar 2010 11:17 On Mar 2, 6:18 pm, Raymond Hettinger <pyt...(a)rcn.com> wrote: > On Mar 2, 8:29 am, Veloz <michaelve...(a)gmail.com> wrote: > > > Hi all > > I'm looking for a queue that I can use with multiprocessing, which has > > a peek method. > > > I've seen some discussion about queue.peek but don't see anything in > > the docs about it. > > > Does python have a queue class with peek semantics? > > Am curious about your use case? Why peek at something > that could be gone by the time you want to use it. > > val = q.peek() > if something_i_want(val): > v2 = q.get() # this could be different than val > > Wouldn't it be better to just get() the value and return if you don't > need it? > > val = q.peek() > if not something_i_want(val): > q.put(val) What I have found myself wanting when thinking of this pattern is a "q.put_at_front_of_queue(val)" method. I've never actually used this because of not having such a method. Not that it's that much of an issue as I've never been completely stuck and usually found a way to solve whatever I was trying to do without peeking, which could be argued as a better design in the first place. I was just wondering if other people ever missed the "q.put_at_front_of_queue()" method or if it is just me. Regards Floris PS: assuming "val = q.get()" on the first line
From: Gregory Ewing on 4 Mar 2010 05:49 Floris Bruynooghe wrote: > I was just wondering if > other people ever missed the "q.put_at_front_of_queue()" method or if > it is just me. Sounds like you don't want a queue, but a stack. Or maybe a double-ended queue. -- Greg
From: Aahz on 8 Mar 2010 20:47
In article <58f61382-ac79-46fb-8612-a3c9fde297dc(a)c16g2000yqd.googlegroups.com>, Veloz <michaelveloz(a)gmail.com> wrote: > >The "peek" parts comes in when the user comes back later to see if >their report has done. That is, in my page controller logic, I'd like >to look through the complete queue and see if the specific report has >been finished (I could tell by matching up the ID of the original >request to the ID in the completed queue). If there was an item in the >queue matching the ID, it would be removed. Here's the question: what happens when the user refreshes the "report done" page? The problem with the way you're doing it is that checking for report done is a one-shot operation. You probably want to use a database to cache this and have some kind of cache expiration. -- Aahz (aahz(a)pythoncraft.com) <*> http://www.pythoncraft.com/ "Many customs in this life persist because they ease friction and promote productivity as a result of universal agreement, and whether they are precisely the optimal choices is much less important." --Henry Spencer |