[Tutor] Removing duplicates in a list with a fixed length of items in the list.

[Kent Johnson]

Adam Cripps wrote:
> I have a list which comprises of simple random arithmetic problems for
> teachers to give to their pupils. This list must be a set length (if
> the teacher asks for 10 questions, they should get 10 questions), but
> should not have any duplicates.
> 
> I've seen the use of sets, but this reduces the size of the list, when
> I have to have a fixed length.
> 
> Is there a quick way of checking if a string is already within a list
> without iterating over the items of the list (which will slow the
> application down slightly)?

Hmm. If you are trying to pick 10 elements at random from a larger list, 
use random.sample(problems, 10)

If for some reason that doesn't work for you (maybe you are creating 
problems on the fly?) you could build a set in a loop, adding items 
until it is the size you want:
problemSet = set()
while len(problemSet) < 10:
   # do something to add a (possibly) new problem to the set

Finally, unless your lists are huge (thousands of items, at a guess) or 
you are doing this very many times (thousands of times), you will not 
notice the time it takes to search the list for duplicates.

Kent