Christoph Zwerschke <[EMAIL PROTECTED]> writes:
> - Because sets can only contain immutable values
Not true. Sets can only contain *hashable* objects, which isn't the
same thing.
> This, of course, in turn raises the question ;-) Would it be desirable
> to have an additional, more general set datatype that can contain
> mutable objects?
You can do that now:
>>> from UserList import UserList
>>> class HashableList(UserList):
... def __hash__(self): return id(self)
...
>>> s = set([HashableList(), HashableList()])
>>> s
set([[], []])
>>> for x in s:
... x.append(3)
...
>>> s
set([[3], [3]])
This also illustrates the danger of this approach, in that I've got
two lists that will compare equal in the same set:
>>> x = list(s)
>>> x[0] == x[1]
True
Of course, in this case the two objets aren't the same, which is what
is required for the mathematical definition of list:
>>> x[0] is x[1]
False
<mike
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Mike Meyer <[EMAIL PROTECTED]> http://www.mired.org/home/mwm/
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