Boolean, If Lesson • 18 min read

Description

Team LEIA

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.

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.

age = int(input("How old are you"))
if age >= 18:
    print("You are a adult")
else:
    print("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”.

IsRaining = True
if IsRaining:
    print("bring an umbrella")
else:
    print("The weather is clear")

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
a = random.randint(0,100)
b = random.randint(0,100)

print(f"a is equal to {a} and b is equal to {b}.")
if a == b:
    print("a equals b")
elif a < b:
    print("a is less than b")
else:
    print("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.
## Import necessary modules
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, valid_responses):
    while True:
        # Print the question
        print("Question: " + prompt)
        # Get user input as the response
        response = input()
        if response in valid_responses:
            return response
        else:
            print("Invalid response. Please enter a valid response.")

# Define the number of questions and initialize the correct answers counter
questions = 6
correct = 0

# Personalized greeting message
# Collect the student's name
user_name = input("Enter your name: ")
print('Hello, ' + user_name + " running " + sys.executable)
print("You will be asked " + str(questions) + " questions.")
answer = input("Are you ready to take a test?")

# Question 1: Boolean Basics 
# Ask a question about Boolean values and check the response
response1 = question_with_response("What is the Boolean value for 'True'? (Enter 'True' or 'False'):", ["True", "False"])
if response1 == "True":
    print("Correct!")
    correct += 1
else:
    print("Incorrect. The correct answer is 'True'.")

# Question 2: Boolean Expressions
# Ask a question about Boolean expressions and their importance in programming
response2 = question_with_response("What does a Boolean expression return? (Enter 'True' or 'False'):", ["True", "False"])
if response2 == "True":
    print("Correct!")
    correct += 1
else:
    print("Incorrect. The correct answer is 'True'.")

# Question 3: Conditional Statements
# Ask a question about the purpose of conditional (if-else) statements in programming
response3 = question_with_response("What is the purpose of conditional (if-else) statements in programming?", ["control the flow of a program"])
print("Correct!")

# Question 4: Relational Operators
# Ask a question about common relational operators in programming and provide examples
response4 = question_with_response("Give an example of a relational operator in programming:", ["<", ">", "<=", ">=", "==", "!="])
print("Correct!")

# Question 5: Logical Operators
# Ask a question about the use of logical operators in programming and provide examples
response5 = question_with_response("What are some common logical operators in programming? (Enter 'and' or 'or'):", ["and", "or"])
print("Correct!")

# Question 6: Python Data Types
# Ask a question about common data types in Python
response6 = question_with_response("What is an example of a numeric data type in Python?", ["int", "float"])
print("Correct!")

# Display the final score
# Calculate the percentage of correct answers and provide feedback
print(user_name + ", you scored " + str(correct) + "/" + str(questions))
percentage = (correct / questions) * 100
print("Your score is " + str(percentage) + "%.")