Output difference from 2 lists of different sizes with words

[Larz60+]

I'd do it this way:

>>> set1 = set(['guava','apple','banana','strawberry','orange'])
>>> set2 = set(['orange','pineapple','apple'])
>>> set3 = set(['banana', 'guava', 'strawberry', 'pineapple'])
>>> set1.difference(set2)
{'strawberry', 'banana', 'guava'}
>>> set3.difference(set1)
{'pineapple'}