lost Hashability with __cmp__

Michael Hudson mwh at python.net
Wed Jan 29 15:33:19 CET 2003


Martin Schmettow <martin.schmettow at bibliothek.uni-regensburg.de> writes:

> Hi all.
> 
> I declared a __cmp__ for a class. Now I get an TypeError: unhashable
> instance if  I use objects of this class as keys in a dictionary.
> Can someone explain why and how I can gain back hashability?

Define a __hash__ method.  Make sure that instances that __cmp__ equal
generate the same hash code.

Cheers,
M.

-- 
112. Computer Science is embarrassed by the computer.
  -- Alan Perlis, http://www.cs.yale.edu/homes/perlis-alan/quotes.html




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