Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.xs4all.nl!newsfeed3a.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; 'handler': 0.05; 'tries': 0.07; 'runs': 0.10; 'python': 0.11; 'def': 0.12; "wouldn't": 0.14; '**kwargs)': 0.16; '**kwargs):': 0.16; '__future__': 0.16; 'c-level': 0.16; 'from:addr:cs': 0.16; 'from:addr:zip.com.au': 0.16; 'from:name:cameron simpson': 0.16; 'handler.': 0.16; 'message-id:@cskk.homeip.net': 0.16; 'ought': 0.16; 'personally,': 0.16; 'received:211.29': 0.16; 'received:211.29.132': 0.16; 'received:cskk.homeip.net': 0.16; 'received:homeip.net': 0.16; 'received:optusnet.com.au': 0.16; 'received:syd.optusnet.com.au': 0.16; 'simpson': 0.16; 'wrote:': 0.18; 'later': 0.20; 'import': 0.22; 'putting': 0.22; 'print': 0.22; 'header:User-Agent:1': 0.23; 'issue,': 0.24; 'cheers,': 0.24; 'header:In-Reply-To:1': 0.27; 'host': 0.29; 'work.': 0.31; 'code': 0.31; 'context.': 0.31; "d'aprano": 0.31; 'ordinary': 0.31; 'work:': 0.31; 'older': 0.33; 'plain': 0.33; 'skip:_ 10': 0.34; 'something': 0.35; 'received:com.au': 0.36; 'charset:us-ascii': 0.36; 'possible': 0.36; 'subject:?': 0.36; 'level': 0.37; 'received:211': 0.38; 'to:addr:python-list': 0.38; 'little': 0.38; 'anything': 0.39; 'to:addr:python.org': 0.39; 'signal': 0.60; 'course': 0.61; 'content-disposition:inline': 0.62; '(that': 0.65; 'close': 0.67; 'believe': 0.68; 'statement,': 0.68; 'prone': 0.91; 'imagine': 0.93 Date: Tue, 12 Aug 2014 16:15:20 +1000 From: Cameron Simpson To: python-list@python.org Subject: Re: Is print thread safe? MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <87k36ee1xo.fsf@elektro.pacujo.net> User-Agent: Mutt/1.5.21 (2010-09-15) References: <87k36ee1xo.fsf@elektro.pacujo.net> X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.1 cv=fvDlOjIf c=1 sm=1 tr=0 a=YuQlxtEQCowy2cfE5kc7TA==:117 a=YuQlxtEQCowy2cfE5kc7TA==:17 a=ZtCCktOnAAAA:8 a=PO7r1zJSAAAA:8 a=LcaDllckn3IA:10 a=PzczSypyshMA:10 a=gyjTKktfeJ0A:10 a=kj9zAlcOel0A:10 a=vrnE16BAAAAA:8 a=KaybevnVAAAA:8 a=kZ7UWmmPAAAA:8 a=6qxQwj5dJAuZdegWAz4A:9 a=CjuIK1q_8ugA:10 a=X5q3X6-Q1Y0A:10 a=pyH5b1fOeEsA:10 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: 34 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1407824124 news.xs4all.nl 2883 [2001:888:2000:d::a6]:49133 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:76100 On 12Aug2014 08:01, Marko Rauhamaa wrote: >Steven D'Aprano : >> Personally, I believe that print ought to do its own locking. And >> print is a statement, although in this case there's no need to support >> anything older than 2.6, so something like this ought to work: >> >> from __future__ import print_function >> >> _print = print >> _rlock = threading.RLock() >> def print(*args, **kwargs): >> with _rlock: >> _print(*args, **kwargs) > >Could this cause a deadlock if print were used in signal handlers? At the C level one tries to do as little as possible in q signal handler. Typically setting a flag or putting something on a queue for later work. In Python that may be a much smaller issue, since I imagine the handler runs in the ordinary course of interpretation, outside the C-level handler context. I personally wouldn't care if this might deadlock in a handler (lots of things might; avoid as many things as possible). Also, the code above uses an RLock; less prone to deadlock than a plain mutex Lock. Cheers, Cameron Simpson A host is a host from coast to coast & no one will talk to a host that's close Unless the host (that isn't close) is busy, hung or dead - David Lesher, wb8foz@skybridge.scl.cwru.edu