Nick Coghlan wrote:
On Thu, May 19, 2011 at 6:43 PM, Nick Coghlan <ncogh...@gmail.com> wrote:
For point 2, I'm personally +0 on the idea of having 1-element bytes
and bytearray objects delegate hashing and comparison operations to
the corresponding integer object. We have the power to make the
obvious code correct code, so let's do that. However, the implications
of the additional key collisions in value based containers may need to
be explored further.
Several folk have said that objects that compare equal must hash equal...
Why? It's an honest question. Here's what I have tried:
--> class Wierd():
... def __init__(self, value):
... self.value = value
... def __eq__(self, other):
... return self.value == other
... def __hash__(self):
... return hash((self.value + 13) ** 3)
...
--> one = Wierd(1)
--> two = Wierd(2)
--> three = Wierd(3)
--> one
<Wierd object at 0x00BFE710>
--> one == 1
True
--> one == 2
False
--> two == 2
True
--> three == 3
True
--> d = dict()
--> d[one] = '1'
--> d[two] = '2'
--> d[three] = '3'
--> d
{<Wierd object at 0x00BFE710>: '1',
<Wierd object at 0x00BFE870>: '3',
<Wierd object at 0x00BFE830>: '2'}
--> d[1] = '1.0'
--> d[2] = '2.0'
--> d[3] = '3.0'
--> d
{<Wierd object at 0x00BFE870>: '3',
1: '1.0',
2: '2.0',
3: '3.0',
<Wierd object at 0x00BFE830>: '2',
<Wierd object at 0x00BFE710>: '1'}
--> d[2]
'2.0'
--> d[two]
'2'
This behavior matches what I was imagining for having
b'a' == 97. They compare equal, yet remain distinct objects
for all other purposes.
If anybody has a link to or an explanation why equal values must be
equal hashes I'm all ears. My apologies in advance if this is an
incredibly naive question.
~Ethan~
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