Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!news-transit.tcx.org.uk!rt.uk.eu.org!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 0.004 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; '__name__': 0.09; 'from:addr:ethan': 0.09; 'from:addr:stoneleaf.us': 0.09; 'from:name:ethan furman': 0.09; 'message-id:@stoneleaf.us': 0.09; 'received:gator410.hostgator.com': 0.09; '~ethan~': 0.09; 'def': 0.13; "'__main__':": 0.16; 'received:72.11': 0.16; 'received:72.11.125': 0.16; 'received:72.11.125.166': 0.16; 'terminate.': 0.16; 'terminates': 0.16; 'wrote:': 0.18; 'trying': 0.21; 'header:In-Reply-To:1': 0.22; 'runs': 0.23; 'module,': 0.23; 'skip:m 30': 0.24; 'string': 0.24; 'import': 0.27; 'tried': 0.27; 'module.': 0.29; 'print': 0.29; 'processes.': 0.30; 'subject:?': 0.31; 'andrew': 0.32; 'idea': 0.32; 'header:User-Agent:1': 0.33; 'to:addr:python-list': 0.34; 'anything': 0.34; 'to:name:python- list': 0.37; 'some': 0.38; 'should': 0.39; 'to:addr:python.org': 0.40; 'received:websitewelcome.com': 0.64; 'received:184': 0.67; 'received:69.56': 0.73; 'subject:this': 0.74; 'idiom': 0.84; 'subject:launch': 0.84 Date: Wed, 21 Dec 2011 11:29:43 -0800 From: Ethan Furman User-Agent: Thunderbird 1.5.0.10 (Windows/20070221) MIME-Version: 1.0 To: python-list Subject: Re: Why does this launch an infinite loop of new processes? References: <4EF22CA1.1070200@gmail.com> In-Reply-To: <4EF22CA1.1070200@gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator410.hostgator.com X-AntiAbuse: Original Domain - python.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - stoneleaf.us X-BWhitelist: no X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: mail.admailinc.com ([192.168.10.136]) [72.11.125.166]:3072 X-Source-Auth: ethan+stoneleaf.us X-Email-Count: 1 X-Source-Cap: dG9idWs7dG9idWs7Z2F0b3I0MTAuaG9zdGdhdG9yLmNvbQ== X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.12 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: 1324497117 news.xs4all.nl 6860 [2001:888:2000:d::a6]:54322 X-Complaints-To: abuse@xs4all.nl Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:17699 Andrew Berg wrote: > I am trying to understand the multiprocessing module, and I tried some > simple code: > > import multiprocessing > def f(): > print('bla bla') > p = multiprocessing.Process(target=f) > p.start() > p.join() > > And the result is a new process that spawns a new process that spawns a > new process ad infinitum until I log out and the OS forcefully > terminates all my user processes. I have no idea what is happening; I > expected it to just print the string and terminate. > Anything that runs at import time should be protected by the `if __name__ == '__main__'` idiom as the children will import the __main__ module. 8<----------------------------------------------- import multiprocessing def f(): print('bla bla') if __name__ == '__main__': p = multiprocessing.Process(target=f) p.start() p.join() 8<----------------------------------------------- ~Ethan~