Path: csiph.com!usenet.pasdenom.info!aioe.org!news.stack.nl!newsfeed.xs4all.nl!newsfeed4.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 0.000 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'example:': 0.03; 'python': 0.09; 'imported': 0.09; 'it;': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'subject:number': 0.09; '2.7': 0.13; '.py': 0.16; '2.7:': 0.16; '3.2.': 0.16; '__pycache__': 0.16; 'clash': 0.16; 'occur.': 0.16; 'received:80.91.229.3': 0.16; 'received:dip.t-dialin.net': 0.16; 'received:plane.gmane.org': 0.16; 'received:t-dialin.net': 0.16; 'wrote:': 0.17; 'compilation': 0.17; 'module': 0.19; 'import': 0.21; '3.2': 0.22; 'subject:problem': 0.22; 'runs': 0.22; 'header:User-Agent:1': 0.26; 'compiled': 0.27; 'header:X-Complaints-To:1': 0.28; 'run': 0.28; 'cat': 0.29; 'python2.7': 0.29; 'unlikely': 0.29; 'probably': 0.29; "i'm": 0.29; 'version,': 0.30; 'file': 0.32; '(2)': 0.32; 'skip:_ 30': 0.32; 'problem': 0.33; 'to:addr:python- list': 0.33; 'code:': 0.33; '(1)': 0.34; 'offered': 0.35; 'received:org': 0.36; 'created': 0.36; 'but': 0.36; 'correctly': 0.37; 'subject:: ': 0.38; 'files': 0.38; 'fact': 0.38; 'to:addr:python.org': 0.39; 'header:Received:5': 0.40; 'world': 0.63; 'more': 0.63; 'due': 0.66; 'subject: ': 0.66; 'execution.': 0.84 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Peter Otten <__peter__@web.de> Subject: Re: Apparent magic number problem Date: Sat, 09 Mar 2013 09:51:31 +0100 Organization: None References: Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7Bit X-Gmane-NNTP-Posting-Host: p5084a829.dip.t-dialin.net User-Agent: KNode/4.7.3 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: 55 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1362819075 news.xs4all.nl 6964 [2001:888:2000:d::a6]:51623 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:40938 Colin J. Williams wrote: > The program runs correctly under each version, but it runs more slowly > under 3.2. > This is probably due to the fact that the .pyc file is created for the > Python 2.7 execution. > When Python 3.2 is run it fails to create a new .pyc file and if the 2.7 > .pyc is offered directly a magic number problem is reported. (1) .pyc files are only created if a module is imported (2) The 2.7 .pyc file is put alongside the .py file whereas the 3.2 .pyc is put into the __pycache__ subfolder. No clash can occur. A simple example: $ ls mod.py $ cat mod.py print("hello world") Run it; no pyc is created: $ python2.7 mod.py hello world $ ls mod.py Import it using 2.7: $ python2.7 -c 'import mod' hello world $ ls mod.py mod.pyc Import it using 3.2: $ python3.2 -c 'import mod' hello world $ ls mod.py mod.pyc __pycache__ $ ls __pycache__/ mod.cpython-32.pyc Run the compiled code: $ python2.7 mod.pyc hello world $ python3.2 __pycache__/mod.cpython-32.pyc hello world But I'm with Steven, it's unlikely that the module compilation phase is responsible for a noticeable slowdown.