'''sets.py

   Jeff Ondich, 1/5/09

   This program illustrates a few operations using Python's
   set data type.
'''

# Build a couple sets
a = set()
a.add('cat')
a.add('emu')
a.add('dog')
a.add('cat') # Note what happens here
print 'a =', a

b = set()
b.add('goat')
b.add('emu')
b.add('moose')
print 'b = ', b

# Do a few operations on the sets.
print 'a intersect b =', a.intersection(b)
print 'a union b =', a.union(b)
print 'a - b =', a.difference(b)
print 'b - a =', b.difference(a)

a.update(b)
print 'a.update(b) turns a into', a