# If there's only one item in the sequence, its value is returned; if the sequence is
# empty, an exception is raised.
# A third argument can be passed to indicate the starting value. In this case the
# starting value is returned for an empty sequence, and the function is first applied
# to the starting value and the first sequence item, then to the result and the next
# item, and so on. For example,
def sum(seq):
def add(x,y): return x+y
return reduce(add, seq, 0)
print sum(range(1, 11))
print sum([])