Antoon Pardon wrote:
> Op 2005-01-10, Bruno Desthuilliers schreef <[EMAIL PROTECTED]>:
>> Antoon Pardon a écrit :
>>> Op 2005-01-08, Bruno Desthuilliers schreef <[EMAIL PROTECTED]>:
>>>
>>>>worzel a écrit :
>>>>
>>>>>I get what the difference is between a tuple and a list, but why would I
>>>>>ever care about the tuple's immuutability?
>>>>
>>>>Because, from a purely pratical POV, only an immutable object can be
>>>>used as kay in a dict.
>>
>><my-bad> s/kay/key/ </my-bad>
>>
>>> This is not true.
>>
>> Chapter and verse, please ?
>
> I don't need chapter and verse. I have already used mutable
> objects as keys and it works just fine.
>
>>>> class hlst(list):
>>>>
>>>> def __hash__(self):
>>>> sum = 0
>>>> for el in self:
>>>> sum += hash(el)
>>>> return sum % 0x37777777
>>>>
Given this hash function, how do you handle changed keys?
.class hlst(list):
. def __hash__(self):
. sum = 0
. for el in self:
. sum += hash(el)
. return sum % 0x37777777
.
.lst = hlst([1,2,3])
.
.d = {}
.d[lst] = 1
.
.lst[0] = 0
.
.print d
.try:
. print d[hlst([0,2,3])]
.except KeyError:
. print "0,2,3: KeyError"
.try:
. print d[hlst([1,2,3])]
.except KeyError:
. print "1,2,3: KeyError"
raises the KeyError twice. How do you access the element then?
And if you can't access the element when it's changed, what is the
advantage over using tuples?
Reinhold
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