In the spirit of heapq for lists, this module provides 
set operations for dictionaries.

Virtues:
-- lightweight, fast, and easy to learn
-- works well with any iterable input
-- takes advantage of the existing implementation

Vices:
-- does not support sets of sets
-- need to wrap sets in list() before displaying
-- no operators

This lightweight module (80 lines of code) is meant to 
be a convenient, fast solution for daily tasks which do 
not require the full firepower of the heavyweight Sets 
module.

Examples
--------
print 'IsSet', isset('factoid'), isset('misinformation')
print 'Equals', equals('algorithm','logarithm'), equals
('sin','cos')
print 'Subset', issubset('heart', 'thread'), issubset
('treat','tryst')
a = 'abracadabra'
b = 'alacazam'
print 'Union', list(union(a,b))
print 'Intersection', list(intersection(a,b))
print 'Difference', list(difference(a,b))
print 'SymmetricDifference', list(symmetric_difference
(a,b))
print 'Uniquification', list(set(a))
print 'Cardinality', len(set(a))
print 'Iteration', [letter.upper() for letter in set(a)]
print 'Membership', 'b' in set(a), 'e' in set(a)