5.1 Decision statements

5.1a What are Python decision statements

Decision statements in Python allow a program to execute certain pieces of code based on specific conditions. The primary decision statements are if, elif, and else.

• if statement: This statement checks a condition. If the condition is true, the code block inside the if statement is executed.

• elif statement: This stands for "else if" and provides additional conditions to check if the initial if condition is false. You can have multiple elif statements to check multiple conditions.

• else statement: This statement is executed if none of the previous conditions (if or elif) are true.

5.1b Why do we use decision statements?

Decision statements are essential for controlling the flow of a program. They allow programs to make decisions and execute specific code blocks based on different conditions, enabling more complex and dynamic behavior.-

Here’s a simple example to demonstrate how if, elif, and else statements work in Python:

Example 5.1.1 - Example of decision statements

age = 14

if age < 13:
    print("You are a child.")
elif age >= 13 and age < 20:
    print("You are a teenager.")
else:
    print("You are an adult.")

You are a teenager.

Example 5.1.1 - Explanation

• if age < 13: - This checks if the value of age is less than 13. If true, it prints "You are a child.".

• elif age >= 13 and age < 20 - If the if condition is false, this checks if the value of age is between 13 and 19 (inclusive). If true, it prints "You are a teenager.".

• else - If neither the if nor the elif conditions are true, this block is executed, printing "You are an adult.".