Boolean

  • A Boolean value is either true or false.
  • A Boolean expression produces a Boolean value (true or false) when evaluated.

Conditional ("if") statements

  • Affect the sequential flow of control by executing different statements based on the value of a Boolean expression.
IF (condition)
{
	<block of statements>
}

The code in <block of statements> is executed if the Boolean expression condition evaluates to true; no action is taken if condition evaluates to false.

IF (condition)
{
	<block of statements>
}
ELSE
{
	<second block of statements>
}

The code in the first <block of statements> is executed if the Boolean expression condition evaluates to true; otherwise, the code in <second block of statements> is executed.

  Cell In[1], line 3
    <block of statements>
    ^
SyntaxError: invalid syntax

Example: Calculate the sum of 2 numbers. If the sum is greater than 10, display 10; otherwise, display the sum.

num1 = INPUT
num2 = INPUT
sum = num1 + num2
IF (sum > 10)
{
	DISPLAY (10)
}
ELSE
{
	DISPLAY (sum)
}

Hack 1

  • Add a variable that represents an age.

  • Add an ‘if’ and ‘print’ function that says “You are an adult” if your age is greater than or equal to 18.

  • Make a function that prints “You are a minor” with the else function.

## YOUR CODE HERE
# Step 1: Add a variable that represents an age
age = 16

if age >= 18:
    print("You are an adult")

else:
    print("You are a minor")

You are a minor

Relational operators:

  • Used to test the relationship between 2 variables, expressions, or values. These relational operators are used for comparisons and they evaluate to a Boolean value (true or false).

Ex. a == b evaluates to true if a and b are equal, otherwise evaluates to false

  • a == b (equals)
  • a != b (not equal to)
  • a > b (greater than)
  • a < b (less than)
  • a >= b (greater than or equal to)
  • a <= b (less than or equal to)

Example: The legal age to work in California is 14 years old. How would we write a Boolean expression to check if someone is at least 14 years old?

age >= 14

Example: Write a Boolean expression to check if the average of height1, height2, and height3 is at least 65 inches.

(height1 + height2 + height3) / 3 >= 65

Hack 2

  • Make a variable called ‘is_raining’ and set it to ‘True”.

  • Make an if statement that prints “Bring an umbrella!” if it is true

  • Make an else statement that says “The weather is clear”.

is_raining = True

if is_raining:
    print("Bring an umbrella!")

else:
    print("The weather is clear")


Bring an umbrella!

Logical operators:

Used to evaluate multiple conditions to produce a single Boolean value.

  • NOT evaluates to true if condition is false, otherwise evaluates to false
  • AND evaluates to true if both conditions are true, otherwise evaluates to false
  • OR evaluates to true if either condition is true or if both conditions are true, otherwise evaluates to false

Example: You win the game if you score at least 10 points and have 5 lives left or if you score at least 50 points and have more than 0 lives left. Write the Boolean expression for this scenario.

(score >= 10 AND lives == 5) OR (score == 50 AND lives > 0)

Relational and logical operators:

Example: These expressions are all different but will produce the same result.

  • age >= 16
  • age > 16 OR age == 16
  • NOT age < 16

Hack 3

  • Make a function to randomize numbers between 0 and 100 to be assigned to variables a and b using random.randint

  • Print the values of the variables

  • Print the relationship of the variables; a is more than, same as, or less than b

import random

def randomize_numbers():
    a = random.randint(0, 100)
    b = random.randint(0, 100)
    return a, b  

a, b = randomize_numbers()  

print(a)
print(b)

if a > b:
    print("a is greater than b")
elif a == b:  
    print("a equals b")
else:
    print("a is less than b")


91
62
a is greater than b

Homework

Criteria for above 90%:

  • Add more questions relating to Boolean rather than only one per topic (ideas: expand on conditional statements, relational/logical operators)
  • Add a way to organize the user scores (possibly some kind of leaderboard, keep track of high score vs. current score, etc. Get creative!)
  • Remember to test your code to make sure it functions correctly.
##Homework

import getpass  # Module to get the user's name
import sys  # Module to access system-related information

# Function to ask a question and get a response
def question_with_response(prompt, correct_answer):
    # Print the question
    print("Question: " + prompt)
    # Get user input as the response
    response = input("Your Answer: ")
    if response.lower() == correct_answer.lower():
        return True
    else:
        return False

# Leaderboard system
scores = {}

# Define the number of questions and initialize the correct answers counter
questions_count = 5
correct = 0

# Personalized greeting message
# Collect the student's name
user_name = input("Enter your name: ")

if user_name in scores:
    print(f'Welcome back, {user_name}! Your previous score was {scores[user_name]}.')

print('Hello, ' + user_name + ". You will be asked " + str(questions_count) + " questions.")
answer = input("Are you ready to take a test? (yes/no) ")

if answer.lower() == 'yes':
    # Question 1: Boolean Basics 
    if question_with_response("True or False: In Python, Boolean values can only be True or False.", "True"):
        correct += 1
        print("Correct!")
    else:
        print("Wrong. The correct answer is True.")
    
    # Question 2: Boolean Expressions
    if question_with_response("Which of the following evaluates to False? (a) 'True and False' (b) 'True or False'", "a"):
        correct += 1
        print("Correct!")
    else:
        print("Wrong. The correct answer is (a) 'True and False'.")

    # Question 3: Conditional Statements
    if question_with_response("What will be the output of the following code?\nif False:\n  print('Hello')\nelse:\n  print('World')", "World"):
        correct += 1
        print("Correct!")
    else:
        print("Wrong. The correct output is 'World'.")
    
    # Question 4: Relational Operators
    if question_with_response("Which of the following is a relational operator in Python? (a) && (b) <= (c) ||", "b"):
        correct += 1
        print("Correct!")
    else:
        print("Wrong. The correct answer is (b) <=.")

    # Question 5: Logical Operators
    if question_with_response("Which of the following is not a logical operator in Python? (a) and (b) or (c) not (d) &", "d"):
        correct += 1
        print("Correct!")
    else:
        print("Wrong. The correct answer is (d) &.")
    
    # Display the final score
    score = (correct / questions_count) * 100
    print(f"{user_name}, you scored {correct}/{questions_count} which is {score:.2f}%")
    
    # Update the score in leaderboard
    scores[user_name] = score
    print("\n---Leaderboard---")
    sorted_scores = dict(sorted(scores.items(), key=lambda item: item[1], reverse=True))
    for key, value in sorted_scores.items():
        print(f"{key}: {value:.2f}%")
    
else:
    print("Okay, maybe next time!")



Hello, Rayane. You will be asked 5 questions.
Question: True or False: In Python, Boolean values can only be True or False.
Correct!
Question: Which of the following evaluates to False? (a) 'True and False' (b) 'True or False'
Correct!
Question: What will be the output of the following code?
if False:
  print('Hello')
else:
  print('World')
Correct!
Question: Which of the following is a relational operator in Python? (a) && (b) <= (c) ||
Correct!
Question: Which of the following is not a logical operator in Python? (a) and (b) or (c) not (d) &
Correct!
Rayane, you scored 5/5 which is 100.00%

---Leaderboard---
Rayane: 100.00%