Chapter 3
Designing and Using Functions

Mathematicians create functions to make calculations (such as Fahrenheit-to-Celsius conversions) easy to reuse and to make other calculations easier to read because they can use those functions instead of repeatedly writing out equations. Programmers do this too, at least as often as mathematicians. In this chapter we will explore several of the built-in functions that come with Python, and we’ll also show you how to define your own functions.