hash values and equality

[Christian Heimes]

Am 20.05.2011 17:50, schrieb MRAB:
> Is this strictly true? I thought that the hash value, an integer, is
> moduloed (Is that how you spell it? Looks weird!) with the number of
> array elements to give an index into the array, so different hashes
> could give the same index, and objects with different hashes could be
> stored in the same 'bucket'.

I don't think 'moduloed' is an existing word but your description is
mostly correct. The hash of the object and length of the hash table are
used to calculate the position in the hash table. However Python's
implementation doesn't use buckets to reduce memory usage and pointer
dereferencing. If a slot in the hash table is already filled with an
object that is not equal to the new object (a collision), the hash is
shifted and the new slot is checked. The implementation detail is well
described in Modules/dictobject.c.

Christian