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Conditional Statements in Python

Conditional statements in Python allow you to make decisions in your code. They control the flow of execution depending on whether a given condition is True or False.

The if Statement​

The simplest conditional statement is the if statement.

Syntax:

if condition:
    # block of code

Example:

x = 10
if x > 5:
    print("x is greater than 5")

The if...else Statement​

The else block runs when the if condition is False.

x = 3
if x > 5:
    print("x is greater than 5")
else:
    print("x is less than or equal to 5")

Output:

x is less than or equal to 5

The if...elif...else Statement​

elif stands for "else if". It lets you check multiple conditions.

score = 85

if score >= 90:
    print("Grade A")
elif score >= 75:
    print("Grade B")
elif score >= 60:
    print("Grade C")
else:
    print("Grade D")

Nested if Statements​

You can put an if statement inside another if statement.

x = 15
if x > 10:
    if x < 20:
        print("x is between 10 and 20")

Conditional Expressions (Ternary Operator)​

Python has a shorter way to write if...else using ternary expressions.

age = 18
status = "Adult" if age >= 18 else "Minor"
print(status)

Output:

Adult

Logical Operators in Conditions​

You can combine multiple conditions using and, or, and not.

x = 7
if x > 5 and x < 10:
    print("x is between 5 and 10")

if x < 5 or x > 10:
    print("x is outside 5 to 10")

if not x == 8:
    print("x is not 8")

Comparing Multiple Values​

You can check if a value exists in a sequence using in.

fruits = ["apple", "banana", "cherry"]
if "apple" in fruits:
    print("Apple is in the list")

Indentation Rules​

In Python, indentation is important for defining code blocks.

if True:
    print("This is indented correctly")
    print("Still inside if block")
print("Outside if block")

Summary Table​

Statement TypeDescription
ifExecutes a block if condition is True
if...elseExecutes else block if condition is False
if...elif...elseChecks multiple conditions
Nested ifif inside another if
Ternary ExpressionShort form of if...else

Practice Questions​

1. Positive / Negative / Zero Checker​

Write a Python program that takes a number as input and checks whether it is positive, negative, or zero.

2. Odd or Even​

Write a Python program to check whether a number is even or odd.

3. Age Eligibility for Voting​

Write a program to take a person’s age as input and check if they are eligible to vote (18 years or older).

4. Largest of Two Numbers​

Write a Python program that takes two numbers as input and prints the larger number using conditional statements.

5. Largest of Three Numbers​

Write a Python program to find the largest among three numbers entered by the user using if, elif, and else.

6. Grading System​

Write a Python program to take a student's marks as input and print the grade according to the following criteria:

  • Marks ≥ 90 → Grade A
  • Marks ≥ 75 and < 90 → Grade B
  • Marks ≥ 50 and < 75 → Grade C
  • Marks < 50 → Grade F

7. Leap Year Checker​

Write a program to check whether a given year is a leap year or not. (Hint: A year is leap if divisible by 4 but not 100, or divisible by 400)

8. Nested If — Number Range Checker​

Write a program that takes a number as input and:

  • Checks if it's positive.
  • If positive, further checks if it is less than 10, between 10 and 50, or greater than 50.

9. Character Classification​

Write a program to input a single character and check whether it is:

  • a vowel,
  • a consonant,
  • a digit, or
  • a special character.

10. Login Authentication (Simple)​

Write a program that asks the user to enter a username and password.

  • If the username is "admin" and the password is "12345", print “Login Successful”.
  • Otherwise, print “Invalid credentials”.

Conclusion​

Conditional statements are essential for decision-making in programs. Mastering if, elif, and else allows you to control your program's logic effectively.