L6 Conditionals

Imagine you’re deciding what to wear based on the weather. If it’s raining, you take an umbrella; if it’s sunny, you wear sunglasses. This is decision-making, and Python does the same using if-else statements.

Conditional statements allow programs to make choices. Based on certain conditions, the program can run different blocks of code.

💡 Analogy: Conditional statements are like a traffic light—when the light is green, cars go; when it's red, they stop. Computers need a way to make decisions just like we do in real life.

Learning Objectives

By the end of this lesson, you will be able to:

1. Use if, elif, and else statements in Python.

2. Write programs that make decisions based on user input.

3. Use logical operators to combine multiple conditions.

Key Terms

• Conditional statements – Code that makes decisions based on conditions using if, elif, and else.

• if statement – Checks a condition and runs a block of code if the condition is True.

• elif statement – Short for "else if," used when multiple conditions need to be checked in sequence.

• else statement – Runs when all previous conditions are False, providing a default action.

• Indentation – The spaces at the beginning of a line that structure Python code, required for if statements.

Example

age = int(input("Enter your age: "))

if age >= 18:

    print("You are an adult!")

elif age >= 13:

    print("You are a teenager!")

else:

    print("You are a child!")

🛑 Common Mistakes

1. Forgetting indentation: Python relies on indentation to define code blocks. if statements must be indented properly.

2. Using = instead of ==: if x = 10: ❌ (assignment error) vs. if x == 10: ✅ (comparison).