Path: csiph.com!usenet.pasdenom.info!aioe.org!news.stack.nl!newsfeed.xs4all.nl!newsfeed2a.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; 'output': 0.05; 'affected': 0.07; 'mentioned,': 0.07; 'python3': 0.07; 'report.': 0.07; 'subject:bug': 0.07; 'friday,': 0.09; 'mixed': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'rejected': 0.09; 'skip:/ 10': 0.09; 'python': 0.11; 'bug': 0.12; "'.html',": 0.16; '(relatively': 0.16; ':-/': 0.16; 'dictionary.': 0.16; 'element.': 0.16; 'internally': 0.16; 'mimetypes': 0.16; 'received:80.91.229.3': 0.16; 'received:dip0.t-ipconnect.de': 0.16; 'received:plane.gmane.org': 0.16; 'received:t-ipconnect.de': 0.16; 'subject:skip:m 10': 0.16; 'wrote:': 0.18; 'module': 0.19; 'seems': 0.21; 'import': 0.22; 'header:User-Agent:1': 0.23; 'commands,': 0.24; "i've": 0.25; 'extension': 0.26; 'query': 0.26; 'header:X-Complaints-To:1': 0.27; 'function': 0.29; "i'm": 0.30; "skip:' 10": 0.31; 'bunch': 0.31; 'probability': 0.31; 'file': 0.32; 'skip:m 30': 0.32; 'linux': 0.33; 'running': 0.33; "i'd": 0.34; 'could': 0.34; 'subject:with': 0.35; 'but': 0.35; 'functions.': 0.36; 'leads': 0.36; 'sequence': 0.36; 'should': 0.36; 'las': 0.37; 'two': 0.37; 'list': 0.37; 'expected': 0.38; 'depends': 0.38; 'skip:m 40': 0.38; 'stable': 0.38; 'to:addr :python-list': 0.38; 'sure': 0.39; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'even': 0.60; 'read': 0.60; 'first': 0.61; 'group,': 0.63; 'skip:n 10': 0.64; 'believe': 0.68; 'of:': 0.68; 'therefore': 0.72; 'guaranteed': 0.75; 'behavior': 0.77; '50%': 0.78; 'dict,': 0.84; 'extensions.': 0.84; 'guessed': 0.84; 'subject:Possible': 0.84; '2013,': 0.91 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Peter Otten <__peter__@web.de> Subject: Re: Possible bug with stability of mimetypes.guess_* function output Date: Fri, 07 Feb 2014 20:40:06 +0100 Organization: None References: <03a2c4c8-313f-4382-8be9-5163d8bf644c@googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7Bit X-Gmane-NNTP-Posting-Host: p57bdb160.dip0.t-ipconnect.de 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: 69 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1391802017 news.xs4all.nl 2843 [2001:888:2000:d::a6]:48831 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:65608 Asaf Las wrote: > On Friday, February 7, 2014 8:06:36 PM UTC+2, Johannes Bauer wrote: >> Hi group, >> >> I'm using Python 3.3.2+ (default, Oct 9 2013, 14:50:09) [GCC 4.8.1] on >> linux and have found what is very peculiar behavior at best and a bug at >> worst. It regards the mimetypes module and in particular the >> guess_all_extensions and guess_extension functions. >> >> I've found that these do not return stable output. When running the >> following commands, it returns one of: >> >> $ python3 -c 'import mimetypes; >> print(mimetypes.guess_all_extensions("text/html"), >> mimetypes.guess_extension("text/html"))' >> ['.htm', '.html', '.shtml'] .htm >> >> $ python3 -c 'import mimetypes; >> print(mimetypes.guess_all_extensions("text/html"), >> mimetypes.guess_extension("text/html"))' >> ['.html', '.htm', '.shtml'] .html >> >> So guess_extension(x) seems to always return guess_all_extensions(x)[0]. >> >> Curiously, "shtml" is never the first element. The other two are mixed >> with a probability of around 50% which leads me to believe they're >> internally managed as a set and are therefore affected by the >> (relatively new) nondeterministic hashing function initialization. >> >> >> I don't know if stable output is guaranteed for these functions, but it >> sure would be nice. Messes up a whole bunch of things otherwise :-/ >> >> Please let me know if this is a bug or expected behavior. >> >> Best regards, >> >> Johannes > > dictionary. same for v3.3.3 as well. > > it might be you could try to query using sequence below : > > import mimetypes > mimetypes.init() > mimetypes.guess_extension("text/html") > > i got only 'htm' for 5 consequitive attempts As Johannes mentioned, this depends on the hash seed: $ PYTHONHASHSEED=0 python3 -c 'print({".htm", ".html", ".shtml"}.pop())' .html $ PYTHONHASHSEED=1 python3 -c 'print({".htm", ".html", ".shtml"}.pop())' .htm $ PYTHONHASHSEED=2 python3 -c 'print({".htm", ".html", ".shtml"}.pop())' .shtml You never see ".shtml" as the guessed extension because it is not in the original mimetypes.types_map dict, but instead programmaticaly read from a file like /etc/mime.types and then added to a list of extensions. Johanes, I'd like the guessed extension to be consistent, too, but even if that is rejected the current behaviour should be documented. Please file a bug report.