Logical operators in Python - Mini Project: Build & Apply

Using Logical Operators in Python

📖 Scenario: You are helping a small store decide if a customer qualifies for a special discount based on their age and membership status.

🎯 Goal: Build a program that uses logical operators to check if a customer is either a member or an adult, and then print if they qualify for the discount.

📋 What You'll Learn

Create a dictionary with customer names as keys and their ages as values

Create a set of members containing the names of customers who are members

Use logical operators and, or, and not to check conditions

Print the qualification result for each customer

💡 Why This Matters

🌍 Real World

Stores often give discounts based on membership or age. This program helps decide who gets a discount.

💼 Career

Understanding logical operators and data structures is key for roles in software development, data analysis, and automation.

1

Create the customer data

Create a dictionary called customers with these exact entries: 'Alice': 17, 'Bob': 20, 'Charlie': 16, 'Diana': 22

Python

# Create the customers dictionary with exact entries
# Your code here

Hint

Use curly braces {} to create the dictionary with the exact names and ages.

2

Create the members set

Create a set called members containing the exact names 'Alice' and 'Diana'

Python

customers = {'Alice': 17, 'Bob': 20, 'Charlie': 16, 'Diana': 22}
# Create the members set with 'Alice' and 'Diana'
# Your code here

Hint

Use curly braces {} to create a set with the exact member names.

3

Check discount qualification using logical operators

Write a for loop using variables name and age to iterate over customers.items(). Inside the loop, create a variable qualifies that is True if the customer is either in members or their age is 18 or more, using the or operator. Use the not operator to check if the customer is not a member and under 18.

Python

customers = {'Alice': 17, 'Bob': 20, 'Charlie': 16, 'Diana': 22}
members = {'Alice', 'Diana'}
# Use a for loop with name and age to iterate over customers.items()
# Inside the loop, create qualifies using logical operators
# Your code here

Hint

Use or to check if the customer is a member or adult. Use not and and to check if they are not a member and under 18.

4

Print the qualification results

Inside the for loop, write a print statement that outputs exactly: "Alice qualifies for discount: true" (replace Alice with the name variable and true with the qualifies variable) for each customer.

Python

customers = {'Alice': 17, 'Bob': 20, 'Charlie': 16, 'Diana': 22}
members = {'Alice', 'Diana'}
for name, age in customers.items():
    qualifies = (name in members) or (age >= 18)
    not_member_and_underage = (not (name in members)) and (age < 18)
    # Print the qualification result for each customer
    # Your code here

Hint

Use an f-string in the print statement to show the name and qualification status.

Practice

1. Which logical operator in Python returns True only if both conditions are true?

easy

A. or

B. xor

C. not

D. and

Solution

1. Step 1: Understand the meaning of logical operators

   The and operator returns True only if both conditions are true.

2. Step 2: Compare with other operators

   or returns True if any condition is true, not reverses a condition, and xor is not a Python keyword.

3. Final Answer:

   and -> Option D

4. Quick Check:

   Both true conditions = and [OK]

Hint: Use 'and' when all conditions must be true [OK]

Common Mistakes:

• Confusing 'and' with 'or'
• Thinking 'not' combines conditions
• Using 'xor' which is not a Python keyword

2. Which of the following is the correct syntax to check if x is NOT equal to 10 using logical operators?

easy

A. not x = 10

B. not (x == 10)

C. x != 10

D. x not= 10

Solution

1. Step 1: Understand how to negate a condition

   The not operator reverses a condition. To check if x is not equal to 10, negate x == 10.

2. Step 2: Check syntax correctness

   not (x == 10) is correct syntax. x != 10 is also correct but not using logical operators explicitly. Other options have syntax errors.

3. Final Answer:

   not (x == 10) -> Option B

4. Quick Check:

   Use 'not' with parentheses for negation [OK]

Hint: Use 'not (condition)' to reverse it properly [OK]

Common Mistakes:

• Writing 'not x = 10' (invalid syntax)
• Using 'x not= 10' (invalid operator)
• Confusing '!=' with 'not' operator usage

3. What is the output of the following code?

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

medium

A. True

B. False

C. SyntaxError

D. None

Solution

1. Step 1: Evaluate each condition

   5 > 3 is True, 2 == 2 is True, 4 < 1 is False.

2. Step 2: Apply logical operators step-by-step

   (5 > 3) and (2 == 2) is True and True = True.
   Then not (4 < 1) is not False = True.
   Finally, True or True = True.

3. Final Answer:

   True -> Option A

4. Quick Check:

   True and True or True = True [OK]

Hint: Evaluate 'and' before 'or', then apply 'not' [OK]

Common Mistakes:

• Ignoring operator precedence
• Misinterpreting 'not' effect
• Assuming 'or' has higher priority than 'and'

4. Find the error in this code snippet:

if not x > 10 and < 5:
    print("Valid")

medium

A. Syntax error due to incomplete condition after 'and'

B. Incorrect use of 'not' operator

C. Missing parentheses around conditions

D. No error, code runs fine

Solution

1. Step 1: Analyze the condition after 'and'

   The condition after and is just < 5, which is incomplete because it lacks a variable to compare.

2. Step 2: Identify syntax error

   Python expects a full condition after and. This causes a syntax error.

3. Final Answer:

   Syntax error due to incomplete condition after 'and' -> Option A

4. Quick Check:

   Conditions must be complete after logical operators [OK]

Hint: Check each condition is complete after 'and' or 'or' [OK]

Common Mistakes:

• Assuming 'not' applies to both conditions
• Ignoring incomplete condition after 'and'
• Missing variable in second condition

5. You want to check if a number n is between 10 and 20 (inclusive) or exactly 0. Which condition correctly uses logical operators?

hard

A. not (n < 10 or n > 20) and n == 0

B. n >= 10 and (n <= 20 or n == 0)

C. (n >= 10 and n <= 20) or n == 0

D. n >= 10 or n <= 20 and n == 0

Solution

1. Step 1: Understand the condition requirements

   The number n should be between 10 and 20 inclusive, or exactly 0.

2. Step 2: Analyze each option

   (n >= 10 and n <= 20) or n == 0 correctly groups the range check with and and then uses or for the zero check.
   n >= 10 and (n <= 20 or n == 0) changes the logic, allowing n == 0 to be combined incorrectly.
   n >= 10 or n <= 20 and n == 0 mixes operators without parentheses, causing wrong logic.
   not (n < 10 or n > 20) and n == 0 incorrectly requires n to be zero and in the range simultaneously.

3. Final Answer:

   (n >= 10 and n <= 20) or n == 0 -> Option C

4. Quick Check:

   Range check with 'and', zero check with 'or' [OK]

Hint: Group range with 'and', combine with 'or' for zero [OK]

Common Mistakes:

• Wrong operator precedence
• Misplacing parentheses
• Combining conditions incorrectly