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Groups > comp.lang.python > #65603

Possible bug with stability of mimetypes.guess_* function output

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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

-- 
>> Wo hattest Du das Beben nochmal GENAU vorhergesagt?
> Zumindest nicht öffentlich!
Ah, der neueste und bis heute genialste Streich unsere großen
Kosmologen: Die Geheim-Vorhersage.
 - Karl Kaos über Rüdiger Thomas in dsa <hidbv3$om2$1@speranza.aioe.org>

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Possible bug with stability of mimetypes.guess_* function output Johannes Bauer <dfnsonfsduifb@gmx.de> - 2014-02-07 19:06 +0100
  Re: Possible bug with stability of mimetypes.guess_* function output Asaf Las <roegltd@gmail.com> - 2014-02-07 11:09 -0800
    Re: Possible bug with stability of mimetypes.guess_* function output Asaf Las <roegltd@gmail.com> - 2014-02-07 11:17 -0800
      Re: Possible bug with stability of mimetypes.guess_* function output Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-02-07 19:28 +0000
    Re: Possible bug with stability of mimetypes.guess_* function output Johannes Bauer <dfnsonfsduifb@gmx.de> - 2014-02-07 20:39 +0100
    Re: Possible bug with stability of mimetypes.guess_* function output Peter Otten <__peter__@web.de> - 2014-02-07 20:40 +0100
      Re: Possible bug with stability of mimetypes.guess_* function output Asaf Las <roegltd@gmail.com> - 2014-02-07 12:25 -0800
        Re: Possible bug with stability of mimetypes.guess_* function output Peter Otten <__peter__@web.de> - 2014-02-08 08:51 +0100
          Re: Possible bug with stability of mimetypes.guess_* function output Asaf Las <roegltd@gmail.com> - 2014-02-08 00:24 -0800
            Re: Possible bug with stability of mimetypes.guess_* function output Peter Otten <__peter__@web.de> - 2014-02-08 09:39 +0100
              Re: Possible bug with stability of mimetypes.guess_* function output Asaf Las <roegltd@gmail.com> - 2014-02-08 02:59 -0800

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