hash values and equality

[Chris Kaynor]

On Fri, May 20, 2011 at 9:20 AM, Chris Angelico <rosuav at gmail.com> wrote:

> On Sat, May 21, 2011 at 1:50 AM, MRAB <python at mrabarnett.plus.com> wrote:
> > [snip]
> > 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'.
>
> There can always be hash collisions between different objects, but the
> assumption is that two identical objects will _always_ "collide".


I think the question was: can this dummy code ever produce a set containing
less then itemCount items (for 0 < itemCount < 2**32)?

itemCount = 100

import itertools

counter = itertools.count().next

class Test(object):

def __init__(self):

self.hash = counter()

def __hash__(self):

 return self.hash

def __eq__(self, other):

return True


set((Test() for i in xrange(itemCount)))




>  Chris Angelico
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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