Loops are one of the fundamental constructs that enable us to control the flow of our program. A for loop is a type of loop that repeats a block of code a specific number of times.

A for loop in Python follows this structure:

for i in range(COUNT):
    code to execute COUNT number of times

The range() function has a few default settings:

• The initial value of i is 0
• i is incremented by 1 each time.

Take a moment to walk through the slides to see this in action.

Note that the value of i goes from 0 up to but not including the number in range.

Customize with the Range Function

A cool thing about the range() function is that you can add parameters to customize your loop:

for i in range(initial, end, increment)

Initial is the starting value, end is the ending value (remember that this number is not included in your loop!), and increment is the amount i is increased each time.

Take a look at the examples to see how you can use parameters to customize a for loop.

• Can you change the for loop to increase by 5 instead of by 2?
• Can you change the for loop to go from 10 to 100?
• What happens when you delete the third parameter?
• Can you have a negative number as an increment?
• What happens if your end value is smaller than your initial value?

Practice #1

Write a program that prints out the multiples of 5 from 5 to 30. You should use one for loop with parameters. Your output should look like this:

5
10
15
20
25
30