[Python-Dev] eq vs hash (original) (raw)

Daniel Krech eikeon at eikeon.com
Sat Apr 5 18:48:21 CEST 2008

On Apr 4, 2008, at 10:38 AM, Guido van Rossum wrote:

On Fri, Apr 4, 2008 at 2:46 AM, Ralf Schmitt <schmir at gmail.com> wrote:

the news file for python 2.6 does not mention that you need to define hash in case you define eq for a class. This breaks some code (for me: mercurial and pyparsing). Shouldn't this be documented somewhere (I also cannot find it in the whatsnew file). Well, technically this has always been the requirement. What specific code breaks? Maybe we need to turn this into a warning in order to be more backwards compatible?

I think a warning would be nice. I've run into a number of places that
are breaking due to the change. Including parts of the standard lib,
in particular, unittest.TestSuite as used by nose [1].

There is already an open issue with patches for this in the issue
tracker [2]. I've been running trunk with the patch installed and am
able to get past the breakage due to the change. I don't believe the
current patch is kicking out a warning however.

[1] http://code.google.com/p/python-nose/issues/detail?id=161 [2] http://bugs.python.org/issue2235

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