Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!feeder.erje.net!newsfeed.xs4all.nl!newsfeed5.news.xs4all.nl!xs4all!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 0.000 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; '(although': 0.05; 'cpython': 0.05; 'exec': 0.07; 'python': 0.08; '>>>>': 0.09; 'dict': 0.09; 'executes': 0.09; 'from:addr:ethan': 0.09; 'from:addr:stoneleaf.us': 0.09; 'from:name:ethan furman': 0.09; 'match.': 0.09; 'message-id:@stoneleaf.us': 0.09; 'received:gator410.hostgator.com': 0.09; 'variables.': 0.09; '~ethan~': 0.09; 'def': 0.13; "hasn't": 0.13; 'cc:addr:python- list': 0.15; 'compiler,': 0.16; 'dictionary,': 0.16; 'frame,': 0.16; 'received:72.11': 0.16; 'received:72.11.125': 0.16; 'received:72.11.125.166': 0.16; 'wrote:': 0.16; 'subject:Question': 0.19; 'header:In-Reply-To:1': 0.22; 'figure': 0.23; 'assigning': 0.23; 'fine': 0.24; 'stack': 0.24; 'function': 0.27; 'variable': 0.27; 'problem': 0.29; 'print': 0.29; 'cc:addr:python.org': 0.29; 'kelly': 0.30; 'operation.': 0.30; 'actually': 0.32; 'does': 0.32; 'actual': 0.32; "can't": 0.32; 'header:User-Agent:1': 0.33; 'setting': 0.34; 'probably': 0.35; '...': 0.35; 'cc:2**1': 0.36; 'but': 0.37; 'happens': 0.37; 'should': 0.38; 'subject:: ': 0.39; 'change': 0.40; 'course,': 0.61; 'received:websitewelcome.com': 0.64; 'believe': 0.65; 'received:184': 0.67; 'subject:name': 0.67; 'hand,': 0.76; 'compiles': 0.84; 'locals': 0.84 Date: Wed, 01 Feb 2012 14:24:28 -0800 From: Ethan Furman User-Agent: Thunderbird 1.5.0.10 (Windows/20070221) MIME-Version: 1.0 To: Ian Kelly Subject: Re: Question about name scope References: <20120201181117.5d35dddc@bigfoot.com> In-Reply-To: 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]:2519 X-Source-Auth: ethan+stoneleaf.us X-Email-Count: 1 X-Source-Cap: dG9idWs7dG9idWs7Z2F0b3I0MTAuaG9zdGdhdG9yLmNvbQ== Cc: python-list@python.org, mwilson@the-wire.com 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: 26 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1328136693 news.xs4all.nl 6871 [2001:888:2000:d::a6]:54593 X-Complaints-To: abuse@xs4all.nl Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:19747 Ian Kelly wrote: > I am not a dev, but I believe it works because assigning to locals() > and assigning via exec are not the same thing. The problem with > assigning to locals() is that you're fundamentally just setting a > value in a dictionary, and even though it happens to be the locals > dict for the stack frame, Python can't figure out that it should go > and update the value of the optimized local to match. exec, on the > other hand, compiles and executes an actual STORE_NAME operation. Of > course, if the particular local variable hasn't been optimized by the > compiler, then updating locals() works just fine (although you > probably should not rely on this): > >>>> def f(x, y): > ... locals()[x] = y > ... print locals()[x] > ... exec 'print ' + x > ... >>>> f('a', 42) > 42 > 42 Definitely should rely on it, because in CPython 3 exec does not un-optimize the function and assigning to locals() will not actually change the functions variables. ~Ethan~