5.7. Iteration¶

Iteration allows us to do things many times, or to process a collection of elements. We’ll look at collections shortly, for now let us just focus on the basics of iteration.

Now this is not very exciting, but suppose we want to build a table that has a row for each number from 0 through 9.

Before you keep reading...

Runestone Academy can only continue if we get support from individuals like you. As a student you are well aware of the high cost of textbooks. Our mission is to provide great books to you for free, but we ask that you consider a $10 donation, more if you can or less if $10 is a burden.

Support Runestone Academy Today

Now that was pretty simple, but it illustrates a very important aspect of programming. The key aspects of the example are:

The for statement, is the statement that allows us to do things many times.
The number of times we do something is controlled by the three statements: 1. i = 0 this is our starting value 2. i < 10 this is our stopping condition. We will keep doing whatever is inside the for statement until i < 10 is no longer true. 3. i++ this is really important as it changes the value of i and allows us to make progress towards the end. Without this third component, i would never increase and we would do whatever is inside the loop forever. This is called an infinite loop.

Now let us look at how we can use the loop to add 10 rows to a table.