The Fibonacci series of numbers was used by Leonardo of Pisa, a.k.a. Fibonacci (around the year 1200), to describe the growth of a rabbit population. The series has been noted to appear in biological settings, such as the branching patterns of leaves in grasses and flowers. We take a look at two different ways Python can get you these numbers. The generator function will add the next number to the series each time it is called. The recursive function gives the Fabonacci value for the parameter given.