Path: csiph.com!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder1.enfer-du-nord.net!feeds.phibee-telecom.net!newsfeed.xs4all.nl!newsfeed3.news.xs4all.nl!xs4all!news2.euro.net!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.001 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'puts': 0.07; 'python': 0.09; 'called.': 0.09; 'subject:Why': 0.09; 'thrown': 0.09; 'cc:addr:python-list': 0.10; 'thread': 0.11; 'yet.': 0.13; 'already,': 0.16; 'end-to-end': 0.16; 'from:addr:cs': 0.16; 'from:addr:zip.com.au': 0.16; 'from:name:cameron simpson': 0.16; 'inserting': 0.16; 'message-id:@cskk.homeip.net': 0.16; 'non- empty': 0.16; 'received:202.125.174': 0.16; 'received:202.125.174.133': 0.16; 'received:boardofstudies.nsw.edu.au': 0.16; 'received:cskk.homeip.net': 0.16; 'received:edu.au': 0.16; 'received:harvey.boardofstudies.nsw.edu.au': 0.16; 'received:homeip.net': 0.16; 'received:nsw.edu.au': 0.16; 'run.': 0.16; 'simpson': 0.16; 'wrote:': 0.17; 'appears': 0.18; 'load': 0.19; 'import': 0.21; 'pipe': 0.22; 'cc:2**0': 0.23; 'transfers': 0.23; 'cc:addr:python.org': 0.25; 'header:In-Reply-To:1': 0.25; 'header:User-Agent:1': 0.26; 'appear': 0.26; 'thanks!': 0.26; 'am,': 0.27; 'skip:# 10': 0.27; 'run': 0.28; 'cat': 0.29; 'queue': 0.29; 'objects': 0.29; 'fri,': 0.30; 'anybody': 0.32; 'could': 0.32; 'print': 0.32; 'controlling': 0.33; 'likely': 0.33; 'nov': 0.35; 'subject:?': 0.35; 'there': 0.35; 'but': 0.36; 'received:au': 0.36; "i'll": 0.36; 'should': 0.36; 'charset:us- ascii': 0.36; 'uses': 0.37; 'why': 0.37; 'item': 0.37; 'far': 0.37; 'data': 0.37; 'subject:: ': 0.38; 'some': 0.38; 'help': 0.40; 'end': 0.40; 'content-disposition:inline': 0.60; 'most': 0.61; 'first': 0.61; 'chance': 0.61; 'become': 0.65; 'day': 0.73; 'feeder': 0.84; 'skip:~ 60': 0.84; 'ban': 0.91; 'roads': 0.91 Date: Sat, 24 Nov 2012 09:19:39 +1100 From: Cameron Simpson To: Ian Kelly Subject: Re: Why queue.empty() returns False even after put() is called? MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) References: Cc: Python X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 37 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1353709191 news.xs4all.nl 6861 [2001:888:2000:d::a6]:43574 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:33866 On 23Nov2012 11:53, Ian Kelly wrote: | On Fri, Nov 23, 2012 at 9:57 AM, Peng Yu wrote: | > The empty() returns True even after put() has been called. Why it is | > empty when there some items in it? Could anybody help me understand | > it? Thanks! | > | > ~/linux/test/python/man/library/multiprocessing/Queue/empty$ cat | > main.py | > #!/usr/bin/env python | > | > import multiprocessing | > | > queue = multiprocessing.Queue() | > print queue.empty() | > queue.put(['a', 'b']) | > queue.put(['c', 'd']) | > print queue.empty() | | According to the docs, the Queue uses a background thread to load data into it: | | When a process first puts an item on the queue a feeder thread is | started which transfers objects from a buffer into the pipe. | | Most likely it still appears to be empty because this thread has not | had a chance to run yet. If you try inserting a time.sleep() call, | you should see the queue become non-empty once the background thread | has run. Conversely, might it not appear empty because the objects have been thrown at the pipe already, appearing to have been consumed? Or is there end-to-end handshaking controlling what .empty() tests? (Though again, the far end may have grabbed them already too.) -- Cameron Simpson The ZZR-1100 is not the bike for me, but the day they invent "nerf" roads and ban radars I'll be the first in line......AMCN