Countdown to launch

Is used to repeat an indented section of code underneath the statement a known number of times.

Note The `while` command is used when you don't know how many iterations will be required, but `for` is used when the number of iterations is known.

Although you can use a while loop instead of a for loop as shown in the example below, it is not considered good practice unless the value of counter can be changed by another command in addition to the increment statement.

counter = 0

while counter < 5:

counter = counter + 1 # This is the increment statement.

Defines a range of numbers to be used by a for loop: x is the starting number, y is the finishing number and z is the increment/decrement applied to x to reach y in each iteration.

range(5)

Means the numbers 0 to 4. Note that it is not necessary to state the starting number or the increment if the loop starts at 0 and increases by 1 in each iteration.

Delays the next line of code executing for x number of seconds. Requires import time to access these commands.

import time

Includes functions from a library called `time` in your program. These are date, time and delay functions.