Lesson 1.5

Boolean Expressions and Operators

Agenda

• Due today:
  • Python Essentials Module 1 Quiz
    • if you have joined the class (via invitation sent to your personal email) then I should be able to see your score
  • Assignment 1.5

What is a Boolean?

• A Boolean value is either:
  • True
  • False
• Useful for making decisions in programs

Boolean Expressions

• Expressions that evaluate to True or False
• Examples:
  • 5 > 3 → True
  • 10 == 7 → False
  • 2 + 2 == 4 → True

Comparison Operators

• == equal to
• != not equal to
• > greater than
• < less than
• >= greater than or equal to
• <= less than or equal to

Quick Check

What does each evaluate to?

• 7 > 10
• 3 != 2
• 4 + 1 == 5

Boolean Operators

• Combine comparisons with:
  • and (both must be True)
  • or (at least one must be True)
  • not (flips True/False)

Example

age = 16
print(age > 14 and age < 18)   # True
print(age > 18 or age == 16)   # True
print(not(age == 16))          # False

Practice Together

• Predict the result, then run it:

print(3 < 5 and 10 == 10)
print(7 != 7 or 2 > 1)
print(not(4 <= 4))

Why Booleans Matter

• Used for making choices in code
• Foundation for if statements (next lesson)

Your Turn

Write a boolean expression that:

• Checks if a number is greater than 100
• Checks if two numbers are equal
• Checks if a number is not zero