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Iterating and Making Decisions

"Insanity: doing the same thing over and over again and expecting different results."

– Albert Einstein

In the previous chapter, we looked at Python's built-in data types. Now that you're familiar with data in its many forms and shapes, it's time to start looking at how a program can use it.

According to Wikipedia:

In computer science, control flow (or alternatively, flow of control) refers to the specification of the order in which the individual statements, instructions or function calls of an imperative program are executed or evaluated.

In order to control the flow of a program, we have two main weapons: conditional programming (also known as branching) and looping. We can use them in many different combinations and variations, but in this chapter, instead of going through all the possible forms of those two constructs in a documentation fashion, I'd rather give you the basics and then I'll write a couple of small scripts with you. In the first one, we'll see how to create a rudimentary prime-number generator, while in the second one, we'll see how to apply discounts to customers based on coupons. This way, you should get a better feeling for how conditional programming and looping can be used.

In this chapter, we are going to cover the following:

Conditional programming
Looping in Python
A quick peek at the itertools module