[Python-3000] __hash__ : Problem with either documentation or understanding
charleshixsn at earthlink.net
Wed Jul 30 00:13:22 CEST 2008
"""If a class defines mutable objects and implements a __cmp__() or __eq__()
method, it should not implement __hash__(), since the dictionary
implementation requires that a key’s hash value is immutable (if the object’s
hash value changes, it will be in the wrong hash bucket).
What I had been planning to do was implement a hash code created by hashing a
unique integer, say the sequential order in which the instance of the class
was created. This would be unique and unchanging number, so the explanation
of why __hash__ should not be created seems wrong. Or *could* it be created?
In which case that statement that it shouldn't be created is wrong.
(Or, of course, I'm misunderstanding things.)
More information about the Python-3000