Path: csiph.com!usenet.pasdenom.info!news.albasani.net!news.mixmin.net!feeds.phibee-telecom.net!newsfeed.xs4all.nl!newsfeed6.news.xs4all.nl!xs4all!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; 'else:': 0.03; 'try:': 0.07; 'ugly': 0.07; 'any.': 0.09; 'loop.': 0.09; 'subject:()': 0.09; 'def': 0.10; 'thread': 0.11; '24,': 0.16; 'event.wait()': 0.16; 'fine.': 0.16; 'heapq': 0.16; 'mutex': 0.16; 'oct': 0.16; 'subject:lock': 0.16; 'threading': 0.16; 'wed,': 0.16; 'wrote:': 0.17; 'bit': 0.21; 'import': 0.21; 'header:In-Reply-To:1': 0.25; 'first,': 0.27; 'message-id:@mail.gmail.com': 0.27; 'queue': 0.29; 'skip:q 20': 0.29; 'things,': 0.29; 'skip:_ 10': 0.29; 'probably': 0.29; 'class': 0.29; 'received:209.85.215.46': 0.30; 'skip:s 30': 0.33; 'rid': 0.33; 'to:addr:python-list': 0.33; 'received:google.com': 0.34; 'conditions.': 0.35; 'false': 0.35; 'pm,': 0.35; 'subject:?': 0.35; 'received:209.85': 0.35; 'next': 0.35; 'except': 0.36; 'but': 0.36; 'skip:p 20': 0.36; 'received:209': 0.37; 'subject:: ': 0.38; 'instead': 0.39; 'to:addr:python.org': 0.39; 'header:Received:5': 0.40; 'more': 0.63; 'to:name:python': 0.84 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type; bh=9uE6YXkp5O81xoARFH15d94k0kJiBdLLCpmpGTKvzfI=; b=YjJSI3tLwttAXxQcVojDhAryiEAsmMUojETCFlyqZB/A/p5J/t0usmxmfQPOjpDK2z +m0Lnkr4HzdmyXF2bu4i3/1gSTAwS6AUxaj/tdMQmRGwRPUam6rGx9/1bAGIDeuczjQb mzJ7aH9+nwfHy9jlEmwP8ZVKmUosUe3hAWeJ3uq4tDdan0OWRJZZ7c3ne/0z7x5WFIbU BWMlU907CxIaEOA+w3FDj74aEw/a8uFhXnYb5s8MnKTQ6l4nTvVnxRLVVGE7c62/dti9 2D51u3NfGENfQ/jl7qENuQYYjHLhzzNDoNuPMFs5Stn2z9Qk+TLNDBk3YG3snhZBEdkx mMbQ== MIME-Version: 1.0 In-Reply-To: References: From: Ian Kelly Date: Wed, 24 Oct 2012 15:00:09 -0600 Subject: Re: A lock that prioritizes acquire()s? To: Python Content-Type: text/plain; charset=ISO-8859-1 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: 44 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1351112441 news.xs4all.nl 6963 [2001:888:2000:d::a6]:37288 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:32067 On Wed, Oct 24, 2012 at 2:19 PM, Ian Kelly wrote: > I used a PriorityQueue and Conditions to get rid of the ugly while True loop. Same things, but with Events instead of Conditions. This is just a bit more readable. The PriorityQueue is also probably unnecessary, since it's always accessed with the mutex held. A heapq would be fine. import threading import Queue class PriorityLock(object): def __init__(self): self._is_available = True self._mutex = threading.Lock() self._waiter_queue = Queue.PriorityQueue() def acquire(self, priority=0): self._mutex.acquire() # First, just check the lock. if self._is_available: self._is_available = False self._mutex.release() return True event = threading.Event() self._waiter_queue.put((priority, event)) self._mutex.release() event.wait() # When the event is triggered, we have the lock. return True def release(self): self._mutex.acquire() # Notify the next thread in line, if any. try: _, event = self._waiter_queue.get_nowait() except Queue.Empty: self._is_available = True else: event.set() self._mutex.release()