Hello, Oleg.
> class UnorderedList(list): > def __eq__(self, other): > if not isinstance(other, UnorderedList): > return False > return sorted(self) == sorted(other) > > def __ne__(self, other): > return not self.__eq__(other) > > Do you need more than that? > > Oleg. That's what I had in mind. I think it'd be useful enough to go in the standard library. Now that there's a sample implementation, should I still try to demonstrate why I believe it's worth adding to the stdlib and get support? Cheers, - Gustavo. On Tue, May 18, 2010 at 11:13 PM, Gustavo Narea <m...@gustavonarea.net> wrote: > Hello, everybody. > > I've been searching for a data structure like a tuple/list *but* unordered > -- > like a set, but duplicated elements shouldn't be removed. I have not even > found a recipe, so I'd like to write an implementation and contribute it to > the "collections" module in the standard library. > > This is the situation I have: I have a data structure that represents an > arithmetic/boolean operation. Operations can be commutative, which means > that > the order of their operands don't change the result of the operation. This > is, > the following operations are equivalent: > operation(a, b, c) == operation(c, b, a) == operation(b, a, c) > operation(a, b, a) == operation(a, a, b) == operation(b, a, a) > operation(a, a) == operation(a, a) > > So, I need a type to store the arguments/operands so that if two of these > collections have the same elements with the same multiplicity, they are > equivalent, regardless of the order. > > A multiset is not exactly what I need: I still need to use the elements in > the > order they were given. For example, the logical conjuction (aka "and" > operator) has a left and right operands; I need to evaluate the first/left > one > and, if it returned True, then call the second/right one. They must not be > evaluated in a random order. > > To sum up, it would behave like a tuple or a list, except when it's > compared > with another object: They would be equivalent if they're both unordered > tuples/lists, and have the same elements. There can be mutable and > immutable > editions (UnorderedList and UnorderedTuple, respectively). > > I will write a PEP to elaborate on this if you think it'd be nice to have. > Or, > should I have written the PEP first? > > Cheers, > -- > Gustavo Narea <xri://=Gustavo>. > | Tech blog: =Gustavo/(+blog)/tech ~ About me: =Gustavo/about | >
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