Using Comparison and Relational Operators in Python

Course: Python Programming

Topic: Using Comparison and Relational Operators

Course Link: Python Training Course – JustAcademy

Demo Link: Register for a Free Course Demo

Website: JustAcademy Official Website

1. Introduction to Comparison and Relational Operators

Comparison operators are fundamental components of Python programming. They allow developers to compare two values, variables, or expressions and determine the relationship between them. These operators help a program make decisions based on conditions.

For example, a program can use comparison operators to check whether a student has passed an examination, whether an employee's salary exceeds a specified amount, whether a user is old enough to register for a service, or whether two values are equal.

In Python, comparison operations generally produce Boolean results: True or False. These results can be used in conditional statements, loops, validation logic, filtering, and other programming tasks.

age = 22
minimum_age = 18

print(age >= minimum_age)
print(age == minimum_age)
print(age < minimum_age)

Output:

True
False
False

In this example, Python checks whether the age is at least 18, exactly 18, and below 18. Each expression returns a Boolean result.

2. Learning Objectives

After studying this topic, learners should be able to:

• Understand the purpose of comparison and relational operators.
• Identify all six standard value-comparison operators in Python.
• Compare numeric values, strings, and supported collections.
• Understand the difference between equality and inequality.
• Use comparison operators in conditional statements and loops.
• Combine comparisons with logical operators.
• Write chained comparisons to check multiple conditions.
• Identify common comparison errors and correct them.
• Apply comparisons to real-world programming scenarios.

3. What Are Relational Operators?

Relational operators determine the relationship between two operands. An operand is a value, variable, or expression on which an operator acts.

For example, in 15 > 10, the values 15 and 10 are operands, and > is the relational operator.

Since 15 is greater than 10, the expression evaluates to True.

first_number = 15
second_number = 10

result = first_number > second_number
print(result)

Output:

True

Relational operators are commonly used to implement business rules, eligibility checks, range validation, and decision-making logic.

4. Types of Comparison Operators in Python

Python provides six standard value-comparison operators. They are used to test equality, inequality, and ordering relationships.

5. Equal To Operator (==)

The equal-to operator, represented by ==, checks whether two values are equal. It returns True when the values compare as equal and False otherwise.

This operator is useful for checking usernames, matching values, validating answers, and comparing numerical results.

number1 = 25
number2 = 25
number3 = 30

print(number1 == number2)
print(number1 == number3)

Output:

True
False

Example: Checking a Login Username

stored_username = "admin"
entered_username = "admin"

if entered_username == stored_username:
    print("Username matched")
else:
    print("Invalid username")

Output:

Username matched

Important: The == operator compares values. It is different from the assignment operator =, which assigns a value to a variable.

score = 80       # Assignment
print(score == 80)  # Comparison

Output:

True

6. Not Equal To Operator (!=)

The not-equal-to operator, represented by !=, checks whether two values are different. It returns True when the values are not equal and False when they are equal.

password = "python123"
entered_password = "python456"

print(password != entered_password)

Output:

True

Example: Validating a Status

status = "inactive"

if status != "active":
    print("Account is not active")
else:
    print("Account is active")

Output:

Account is not active

This operator is useful when a program needs to detect mismatched values, reject invalid input, or execute a block of code only when a condition is not satisfied.

7. Greater Than Operator (>)

The greater-than operator checks whether the value on the left is strictly greater than the value on the right. Equality does not satisfy this condition.

salary = 50000
minimum_salary = 40000

print(salary > minimum_salary)
print(minimum_salary > salary)

Output:

True
False

Example: Checking Sales Performance

sales = 75000
target = 60000

if sales > target:
    print("Sales target exceeded")
else:
    print("Sales target not exceeded")

Output:

Sales target exceeded

Use > when a value must exceed a threshold, such as a sales target, minimum balance requirement, or performance benchmark.

8. Less Than Operator (<)

The less-than operator checks whether the left operand is strictly smaller than the right operand. If both values are equal, the result is False.

temperature = 15
limit = 20

print(temperature < limit)
print(temperature < 10)

Output:

True
False

Example: Checking Inventory

stock = 4
reorder_level = 10

if stock < reorder_level:
    print("Restock required")
else:
    print("Stock level is sufficient")

Output:

Restock required

The less-than operator is commonly used in inventory management, temperature monitoring, loop conditions, and threshold-based validation.

9. Greater Than or Equal To Operator (>=)

The greater-than-or-equal-to operator checks whether the left operand is greater than or equal to the right operand. It returns True in either case.

marks = 40
passing_marks = 40

print(marks >= passing_marks)
print(45 >= passing_marks)
print(30 >= passing_marks)

Output:

True
True
False

Example: Exam Eligibility

marks = 68
passing_marks = 40

if marks >= passing_marks:
    print("Student passed")
else:
    print("Student failed")

Output:

Student passed

This operator is especially useful for eligibility checks where the boundary value must also be accepted.

10. Less Than or Equal To Operator (<=)

The less-than-or-equal-to operator checks whether the left operand is smaller than or equal to the right operand.

items = 5
maximum_items = 5

print(items <= maximum_items)
print(3 <= maximum_items)
print(8 <= maximum_items)

Output:

True
True
False

Example: Checking a Spending Limit

purchase_amount = 450
budget_limit = 500

if purchase_amount <= budget_limit:
    print("Purchase is within budget")
else:
    print("Budget exceeded")

Output:

Purchase is within budget

Use this operator when a value must remain below a maximum allowed limit, including budget limits, maximum capacity, and allowed attempt counts.

11. Comparing Numeric Values

Python supports comparison operations on compatible numeric values, including integers and floating-point numbers. Comparisons between numeric types can work even when the types differ.

integer_value = 10
float_value = 10.0

print(integer_value == float_value)
print(12 > 7.5)
print(4.5 < 5)
print(20 != 15)

Output:

True
True
True
True

In the first expression, the integer 10 and floating-point value 10.0 compare as equal numerically.

Working with Decimal Values

Floating-point calculations can sometimes produce small precision differences because many decimal fractions cannot be represented exactly in binary floating-point format.

result = 0.1 + 0.2

print(result)
print(result == 0.3)

Typical output:

0.30000000000000004
False

For approximate floating-point comparisons, use a tolerance when appropriate.

import math

result = 0.1 + 0.2

print(math.isclose(result, 0.3))

Output:

True

12. Comparing Strings

Python supports equality and ordering comparisons for strings. String ordering is lexicographical and is based on Unicode code points, not dictionary rules or language-specific alphabetical conventions.

String comparisons are case-sensitive. Therefore, uppercase and lowercase characters can produce different results.

name1 = "Python"
name2 = "Python"
name3 = "python"

print(name1 == name2)
print(name1 == name3)
print("apple" < "banana")

Output:

True
False
True

Case-Insensitive Comparisons

If a task requires case-insensitive matching, normalize the strings before comparing them.

username1 = "Admin"
username2 = "admin"

print(username1.lower() == username2.lower())

Output:

True

For user-facing text, consider whether whitespace, Unicode normalization, or language-specific sorting rules also need to be handled.

13. Comparing Lists and Tuples

Lists and tuples can be compared for equality. Two lists compare equal when they contain equal corresponding elements in the same order. A list and a tuple with the same visible elements do not compare equal because they are different types.

list1 = [10, 20, 30]
list2 = [10, 20, 30]
list3 = [30, 20, 10]

print(list1 == list2)
print(list1 == list3)
print([1, 2] == (1, 2))

Output:

True
False
False

Lists and tuples also support lexicographical ordering when their corresponding elements support ordering comparisons.

print([1, 2, 3] < [1, 2, 4])
print([1, 2] < [1, 2, 0])

Output:

True
True

Python compares elements from left to right. When it finds the first unequal pair, that comparison determines the ordering. If all shared elements are equal, the shorter sequence is ordered before the longer one.

14. Using Comparison Operators with Conditional Statements

Comparison operators are frequently used with if, elif, and else statements. They allow a program to execute different code depending on whether a condition evaluates to true or false.

Example: Grade Classification

marks = 82

if marks >= 90:
    print("Grade A+")
elif marks >= 80:
    print("Grade A")
elif marks >= 70:
    print("Grade B")
elif marks >= 40:
    print("Grade C")
else:
    print("Fail")

Output:

Grade A

Python checks the conditions from top to bottom and executes the first matching branch. The order of conditions matters when the ranges overlap.

15. Combining Comparisons with Logical Operators

Logical operators can combine comparison expressions to represent more complex conditions.

Example: Eligibility Check

age = 25
has_id = True

if age >= 18 and has_id:
    print("Eligible to register")
else:
    print("Not eligible to register")

Output:

Eligible to register

Logical operators are useful when a rule depends on multiple requirements, such as age, documentation, income, or attendance.

16. Chained Comparisons

Python allows multiple comparison operators to be chained in one expression. This feature is particularly useful for checking whether a value lies within a range.

age = 25

print(18 <= age <= 60)

Output:

True

The expression 18 <= age <= 60 checks both that the age is at least 18 and that it is at most 60. It is equivalent in meaning to 18 <= age and age <= 60, with the middle expression evaluated only once.

More Examples

number = 15

print(10 < number < 20)
print(1 < number < 10)
print(5 <= number <= 15)

Output:

True
False
True

Chained comparisons improve readability when checking numerical ranges and boundaries.

17. Comparison Operators in Loops

Comparison expressions can control when a loop continues or stops. They are often used in while loops and in conditional statements inside for loops.

Example: While Loop

count = 1

while count <= 5:
    print(count)
    count += 1

Output:

1
2
3
4
5

The loop continues while count <= 5 evaluates to True. Once the condition becomes false, the loop terminates.

Example: Filtering Values

numbers = [5, 12, 18, 3, 25, 9]

for number in numbers:
    if number > 10:
        print(number)

Output:

12
18
25

18. Comparison Operators and User Input

The input() function returns text as a string. If you want to compare entered numbers numerically, convert the input into an appropriate numeric type first.

Incorrect Approach

age = input("Enter your age: ")

print(age >= 18)

This code raises a TypeError because it attempts to compare a string with an integer.

Correct Approach

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

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

For robust programs, validate user input and handle invalid values. For example, converting non-numeric text with int() raises a ValueError.

19. Difference Between == and is

The equality operator == compares values, whereas the identity operator is checks whether two references point to the same object.

first = [1, 2, 3]
second = [1, 2, 3]
third = first

print(first == second)
print(first is second)
print(first is third)

Output:

True
False
True

The two separately created lists contain equal values, but they are distinct objects. The variable third refers to the same object as first.

Best practice: Use == for value equality. Use is when identity is what matters, particularly when checking for None.

result = None

if result is None:
    print("No result available")

Output:

No result available

20. Common Mistakes When Using Comparison Operators

21. Practical Real-World Examples

Example 1: ATM Withdrawal

balance = 5000
withdrawal = 2000

if withdrawal > 0 and withdrawal <= balance:
    balance -= withdrawal
    print("Withdrawal successful")
    print("Remaining balance:", balance)
else:
    print("Invalid withdrawal")

Output:

Withdrawal successful
Remaining balance: 3000

Example 2: Discount Eligibility

purchase_amount = 2500

if purchase_amount >= 2000:
    print("You qualify for a discount")
else:
    print("No discount available")

Output:

You qualify for a discount

Example 3: Temperature Monitoring

temperature = 42

if temperature > 40:
    print("High temperature warning")
elif temperature < 10:
    print("Low temperature warning")
else:
    print("Temperature is within the expected range")

Output:

High temperature warning

Example 4: Password Length Validation

password = "python123"

if len(password) >= 8:
    print("Password length is acceptable")
else:
    print("Password must contain at least 8 characters")

Output:

Password length is acceptable

This example checks only password length. A production authentication system should also follow appropriate password-security practices.

22. Practice Exercises

Complete the following exercises to strengthen your understanding of comparison and relational operators.

1. Write a program to compare two integers and display whether they are equal.
2. Write a program that checks whether a number is greater than 100.
3. Write a program that determines whether a student has passed with at least 40 marks.
4. Compare two strings and display whether they match exactly.
5. Write a program that checks whether a number lies between 1 and 100, inclusive.
6. Write a program to check whether a shopping amount qualifies for a discount.
7. Use a while loop to print numbers from 1 to 10.
8. Write a program that checks whether an entered age is within the range of 18 to 60.
9. Compare two lists for equality and explain the output.
10. Demonstrate the difference between == and is using two separate lists.

23. Practice Exercise Solutions

Solution 1: Compare Two Integers

a = 20
b = 20

if a == b:
    print("Both numbers are equal")
else:
    print("Numbers are different")

Solution 2: Check a Number Greater Than 100

number = 150

if number > 100:
    print("Number is greater than 100")
else:
    print("Number is 100 or less")

Solution 3: Check Passing Marks

marks = 55

if marks >= 40:
    print("Pass")
else:
    print("Fail")

Solution 4: Compare Strings

text1 = "Python"
text2 = "Python"

print(text1 == text2)

Solution 5: Check a Range

number = 75

if 1 <= number <= 100:
    print("Number is within the range")
else:
    print("Number is outside the range")

24. Interview Questions and Answers

Q1. What are comparison operators in Python?

Comparison operators compare two values and generally return a Boolean result indicating whether a specified relationship holds.

Q2. What is the difference between == and =?

The == operator checks equality, while = assigns a value to a variable.

Q3. What is the difference between > and >=?

The > operator checks whether the left value is strictly greater. The >= operator also accepts equal values.

Q4. What does the != operator do?

It checks whether two values are not equal.

Q5. What type of result do standard comparison expressions return?

For ordinary built-in value comparisons, the result is a Boolean value: True or False.

Q6. Can strings be compared in Python?

Yes. Strings can be compared for equality and ordering. Ordering follows lexicographical Unicode code-point comparison.

Q7. What is a chained comparison?

A chained comparison combines multiple comparisons, such as 10 <= age <= 60, in a readable expression.

Q8. Why can comparing input with a number cause an error?

The input() function returns a string. Convert it to a suitable numeric type before performing numerical ordering comparisons.

Q9. What is the difference between == and is?

== checks value equality, whereas is checks object identity.

Q10. How are comparison operators used in decision-making?

They evaluate conditions used by if, elif, else, and loops to control program execution.

25. Quick Revision Checklist

• == checks equality.
• != checks inequality.
• > checks whether the left value is greater.
• < checks whether the left value is smaller.
• >= checks whether the left value is greater than or equal.
• <= checks whether the left value is smaller than or equal.
• Comparison expressions are commonly used in conditions and loops.
• Use and, or, and not to build compound conditions.
• Use chained comparisons for readable range checks.
• Use == for value equality and is for object identity.
• Convert user input before comparing it numerically.
• Pay attention to boundaries, data types, and floating-point precision.

26. Conclusion

Comparison and relational operators are essential tools for building meaningful Python programs. They help developers evaluate conditions, compare values, validate user input, filter data, and control program flow.

Understanding the six standard value-comparison operators—==, !=, >, <, >=, and <=—provides a strong foundation for learning conditional statements, loops, logical operators, and more advanced programming concepts.

Regular practice with small programs and real-world examples will help you use these operators confidently and avoid common mistakes.

Learn Python with JustAcademy

Continue learning Python programming concepts and strengthen your practical coding skills through the following resources.

• Explore the Python Training Course
• Register for a Course Demo
• Visit the JustAcademy Website