insert unique data in a list

[knifenomad]

On 12월14일, 오전2시57분, mattia <ger... at gmail.com> wrote:
> Il Sun, 13 Dec 2009 16:37:20 +0000, mattia ha scritto:
>
> > How can I insert non-duplicate data in a list? I mean, is there a
> > particular option in the creation of a list that permit me not to use
> > something like:
> > def append_unique(l, val):
> >     if val not in l:
> >         l.append(val)
>
> > Thanks,
> > Mattia
>
> Ok, so you all suggest to use a set. Now the second question, more
> interesting. Why can't I insert a list into a set? I mean, I have a
> function that returns a list. I call this function several times and
> maybe the list returned is the same as another one already returned. I
> usually put all this lists into another list. How can I assure that my
> list contains only unique lists? Using set does'n work (i.e. the python
> interpreter tells me: TypeError: unhashable type: 'list')...

this makes the set type hashable.

class Set(set):
    __hash__ = lambda self: id(self)

s = Set()
s.add(1)
s.add(2)
s.add(1)

print s
set([1, 2])

d = {}
d[s] = 'voila'

print d
{Set([1,2]):'voila'}

print d[s]
'voila'