comparing values in two sets

[Paul Rubin]

John Salerno <johnjsal at NOSPAMgmail.com> writes:
> I'd like to compare the values in two different sets to test if any of
> the positions in either set share the same value (e.g., if the third
> element of each set is an 'a', then the test fails).

I think by "sets" you mean "lists".  Sets are unordered, as a few
people have mentioned.

> I have this:
> 
> def test_sets(original_set, trans_letters):
>      for pair in zip(original_set, trans_letters):
>          if pair[0] == pair[1]:
>              return False
>      return True

That's fairly reasonable.  You could use itertools.izip instead of
zip, which makes a generator instead of building up a whole new list
in memory.  A more traditional imperative-style version would be
something like:

   def test_sets(original_set, trans_letters):
       for i in xrange(len(original_set)):
           if original_set[i] == trans_letters[i]:
               return True
           return False

You could even get cutesy and say something like (untested):

    from itertools import izip
    def test_sets(original_set, trans_letters):
        return not sum(a==b for a,b in izip(original_set, trans_letters))

but that can be slower since it always scans both lists in entirety,
even if a matching pair of elements is found right away.

I don't offhand see a builtin function or not-too-obscure one-liner
that short-circuits, but maybe there is one.

Note that all the above examples assume the two lists are the same
length.  Otherwise, some adjustment is needed.