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Re: Hash stability

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From Stefan Behnel <stefan_ml@behnel.de>
Subject Re: Hash stability
Date Sun, 15 Jan 2012 11:13:56 +0100
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Heiko Wundram, 14.01.2012 23:45:
> Am 14.01.2012 10:46, schrieb Peter Otten:
>> Steven D'Aprano wrote:
>>> How many people rely on hash(some_string) being stable across Python
>>> versions? Does anyone have code that will be broken if the string hashing
>>> algorithm changes?
>>
>> Nobody who understands the question ;)
> 
> Erm, not exactly true. There are actually some packages out there (take
> suds [https://fedorahosted.org/suds/], for example) that rely on the
> hashing algorithm to be stable to function "properly" (suds uses hash() of
> strings to create caches of objects/XML Schemas on the filesystem).

That's a stupid design. Using a hash function that the application does not
control to index into persistent storage just screams for getting the code
broken at some point.

Stefan

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Thread

Hash stability Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-01-14 04:42 +0000
  Re: Hash stability Peter Otten <__peter__@web.de> - 2012-01-14 10:46 +0100
  Re: Hash stability Heiko Wundram <modelnine@modelnine.org> - 2012-01-14 23:45 +0100
  Re: Hash stability Chris Angelico <rosuav@gmail.com> - 2012-01-15 11:36 +1100
    Re: Hash stability Bryan <bryanjugglercryptographer@yahoo.com> - 2012-01-15 04:03 -0800
      Re: Hash stability Chris Angelico <rosuav@gmail.com> - 2012-01-15 23:21 +1100
  Re: Hash stability Roy Smith <roy@panix.com> - 2012-01-14 21:26 -0500
    Re: Hash stability Terry Reedy <tjreedy@udel.edu> - 2012-01-14 23:07 -0500
  Re: Hash stability Stefan Behnel <stefan_ml@behnel.de> - 2012-01-15 11:13 +0100
  Re: Hash stability Heiko Wundram <modelnine@modelnine.org> - 2012-01-15 12:46 +0100
  Re: Hash stability Peter Otten <__peter__@web.de> - 2012-01-15 13:22 +0100
  Re: Hash stability Heiko Wundram <modelnine@modelnine.org> - 2012-01-15 17:07 +0100
  Re: Hash stability Chris Angelico <rosuav@gmail.com> - 2012-01-16 03:13 +1100
  Re: Hash stability Heiko Wundram <modelnine@modelnine.org> - 2012-01-15 17:51 +0100
  Re: Hash stability Stefan Behnel <stefan_ml@behnel.de> - 2012-01-15 18:20 +0100
  Re: Hash stability Peter Otten <__peter__@web.de> - 2012-01-16 09:18 +0100
  Re: Hash stability Christian Heimes <lists@cheimes.de> - 2012-01-16 09:44 +0100
  Re: Hash stability Heiko Wundram <modelnine@modelnine.org> - 2012-01-16 10:15 +0100

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