# Let's write reusable code, and unit test it.
     def add_money(amounts):
         # do arithmetic in pennies so as not to accumulate float errors
         pennies = sum([round(int(amount * 100)) for amount in amounts])
         return float(pennies / 100.0)
     import unittest
     class TestAddMoney(unittest.TestCase):
         def test_float_errors(self):
             self.failUnlessEqual(add_money([0.13, 0.02]), 0.15)
             self.failUnlessEqual(add_money([100.01, 99.99]), 200)
             self.failUnlessEqual(add_money([0, -13.00, 13.00]), 0)
     if __name__ == '__main__':
         unittest.main()

I believe I've still kept it to 13 lines.

STeVe