import collections


print '************'
x = collections.defaultdict(set)
x[1].update([1])
print 'After initialization: %s' % x
items = x.pop(1)
x[1].update(items)
print 'Popping and updating in two steps: %s' % x

print '************'
y = collections.defaultdict(set)
y[1].update([1])
print 'After initialization: %s' % y
y[1].update(y.pop(1))
print 'Popping and updating in one step: %s' % y