Chapter 4. Functions, the Building Blocks of Code

	"To create architecture is to put in order. Put what in order? Function and objects."
	--Le Corbusier

In this chapter, we're going to explore functions. We already said that everything is an object in Python, and functions are no exception to this. But, what exactly is a function? A function is a sequence of instructions that perform a task, bundled as a unit. This unit can then be imported and used wherever it's needed. There are many advantages to using functions in your code, as we'll see shortly.

I believe the saying, a picture is worth one thousand words, is particularly true when explaining functions to someone who is new to this concept, so please take a look at the following image:

As you can see, a function is a block of instructions, packaged as a whole, like a box. Functions can accept input arguments and produce output values. Both of these are optional, as we'll see in the examples in this chapter.

A function in Python is defined...