[Tutor] Set changing order of items?

[Adam Cripps]

On 1/20/07, Kent Johnson <kent37 at tds.net> wrote:
> Adam Cripps wrote:
> > On 1/19/07, Simon Brunning <simon at brunningonline.net> wrote:
> >> On 1/19/07, Adam Cripps <kabads at gmail.com> wrote:
> >>> I'm adding strings to a Set to prevent duplicates. However, the
> >>> strings are meant to be in the correct order. When I add the string to
> >>> the Set, the order seems to change (and I don't seem to be able to
> >>> predict what order they are in).
> >> Sets, like dictionaries, hold their items in an arbitrary order - see
> >> <http://tinyurl.com/a2nkg>.
> >
> > OK - thanks for that - so it seems that using a Set will complicate
> > the matter more.
> >
> > Really, I want to have a set of sets which won't have any duplicates.
> > An example might look something ilke this:
> >
> > sums = [['1) 10 + 2 =', '12'], ['2) 13 + 4 =', '17']]
> > return sums
> >
> > How might I achieve this list, without the duplicates (the duplicate
> > bit is the bit I'm stuck on).
>
> What is your criterion for uniqueness? Are you looking at just the sum,
> as you mentioned earlier, or the whole problem? Why is the order
> important, since the problems are randomly generated?
>
> You should think about a more abstract way of representing a problem.
> For example, the two problems above could be represented as the tuples
> (10, 2, 12) and (13, 4, 17). If you want the whole problems to be
> unique, then creating a set of tuples like this should do what you want.
> (I used tuples instead of lists because you can't make a set of lists.)
>
> If you want only one problem with a given sum, then I would represent a
> problem as an entry in a dictionary where the sum is the key and the
> value is a tuple containing the two addends. Then you can keep putting
> problems in the dictionary until it is the size you want.
>
> Once you have the final set (or dict) of problems, then you can convert
> them to a string representation and print them.

Many thanks all - I've got there in the end, using a tuple inside a
set, ditching the question number and then rendering the sum for
output in my main gui module.

However, this does raise another issue now (which I had thought would
happen, but was putting it off until I'd solved the original problem).

Basically, the user can choose how many problems are set - i. They can
also choose the highest and lowest possible numbers - highest and
lowest. With these values, they can now create a scenario which will
lock the application - they can choose values with a narrow margin
(lowest = 5, highest = 6) and then choose to have 100 of these
problems (i=100). Of course, this will mean that my app will now go
through that loop trying to find a new combination that no longer is
possible.

Anyone have any guidance or tips here? How will I create a flag which
is raised once the loop becomes infinite?

TIA
Adam
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