In some cases, we might want to extend the numeric tower available in Python. A subclass of numbers.Number may simplify a functional program. We can, for example, isolate parts of a complex algorithm to the Number subclass definition, making other parts of the application simpler or clearer.
Python already offers a rich variety of numeric types. The built-in types of the int and float variables cover a wide variety of problem domains. When working with currency, the decimal.Decimal package handles this elegantly. In some cases, we might find the fractions.Fraction class to be more appropriate than the float variable.
When working with geographic data, for example, we might consider creating a subclass of float variables ...
