Be careful if you decide to use hash.
There is possibility of bugs due to that approach, (if hash(x) == hash(y) and x != y).
Even if the probability of bug is near 0, your computer will certainly recall you what is the murphy law.
If I were you, I would prefer another approach.
Cyril
On 7/19/05, Glauco <[EMAIL PROTECTED]> wrote:
Steven D'Aprano wrote:
> On Mon, 18 Jul 2005 12:17:37 +0200, Glauco wrote:
>
>
>>I want to insert a concept of alias in a dict_based class.
>>
>>The idea is to have a facoltative name in the same dict that correspond
>>at the same value. With this alias i can change original value.
>>
>>example:
>>
>>mydict['a'] = 1
>>I must define an alias example: myFunctAlias( mydict, 'a', 'b')
>>print mydict
>>{'a':1, 'b':1}
>>mydict['b'] = 2
>>print mydict
>>{'a':2, 'b':2}
>>
>>
>>The only idea i have is to implement two dictionary one for convert
>>name, alias in two keys with the same value (eg.numeric) in the first
>>dict. The second for store only one time the k, v .
>
>
> You need some sort of redirection, something like this (untested):
>
> class Doubledict:
> def __init__(self, **kargs):
> self.data = "">> self.aliases = {}
> for key in kargs:
> # Point the key to a hash.
> self.aliases[key] = hash(key)
> # And point the hash at the value.
> self.data[hash(key)] = kargs[key]
>
> def setalias(self, key, alias):
> # Point the alias to the same hash as the real key.
> self.aliases[alias] = hash(key)
>
> def __getitem__(self, key):
> return self.data[self.aliases[key]]
>
> def __setitem__(self, key, value):
> self.data [self.aliases[key]] = value
>
>
> The only niggly worry I have is I'm not sure when hash can be used, when
> it is unique, or even if is it guaranteed to be unique.
>
Thank Steve, the idea was the same...
but yours using hash is much elegant.
Thank you
Glauco
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