There are several possible interpretations of your question.
1) Go through the lists in pairs, stopping when the pair is equal to:
>>> s = [10, 14, 18, 20, 25] >>> t = [55, 42, 18, 12, 4] >>> for x, y in zip(s, t): if x == y: print 'Equal element found:', x break Equal element found: 18
2) Navigate through the list, stopping when any item is equal to any other item in the first list. This is the case when kits are useful (they quickly test membership):
>>> s = {18, 20, 25, 14, 10} >>> for x in t: if x in s: print 'Equal element found', x break Equal element found 18
3) Iterate over the same elements, and compare their values:
>>> s = [10, 14, 18, 20, 25] >>> t = [55, 42, 18, 12, 4] >>> [x==y for x, y in zip(s, t)] [False, False, True, False, False]