Randy Bush wrote:
> for pKey, pVal in dict.iteritems():
> print \
> pKey[0], hash(pKey[0]), \
> pKey[1], hash(pKey[1]), \
> pKey[2], hash(pKey[2]), \
> "hash=", hash(pKey), \
> pVal[0], hash(pVal[0]), \
> pVal[1], hash(pVal[1])
>
> when run with | sort, produces
>
> 12.0.0.0 -2054516913 8 8 7018 329707286 hash= -604503432 917088000 917088000
> 917088000 917088000
> 12.0.0.0 -2054516913 8 8 7018 329707286 hash= -604503432 917088000 917088000
> 917088000 917088000
> 12.0.0.0 -2054516913 8 8 7018 329707286 hash= -604503432 917088000 917088000
> 917088000 917088000
> 12.0.0.0 -2054516913 8 8 7018 329707286 hash= -604503432 917088000 917088000
> 917088000 917088000
> 12.0.0.0 -2054516913 9 -1293912648 7018 329707286 hash= -1578430040 917088000
> 917088000 917088000 917088000
> 12.0.0.0 -2054516913 9 -1293912648 7018 329707286 hash= -1578430040 917088000
> 917088000 917088000 917088000
>
> not that there are two entries with the same hash=
Whatever the hash function is for your keys, it returns the same value
for two different keys. A simple example of this kind of phenomenon:
py> class C(object):
... def __hash__(self):
... return 1
...
py> c1, c2 = C(), C()
py> d = {c1:1, c2:2}
py> for key, value in d.iteritems():
... print hash(key), key, value
...
1 <__main__.C object at 0x0126CCD0> 1
1 <__main__.C object at 0x012739D0> 2
Note that the hashes are the same. But are the objects the same?
py> c1 == c2
False
Nope. (This is because the default __eq__ method compares the ids of
the two objects, and as you can see, they have different ids.)
The point is this: you can have multiple objects in the same dict that
have the same hash(), as long as none of those objects equals another.
For more information, see:
http://wiki.python.org/moin/DictionaryKeys
STeVe
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