Conditional Statements in Python

Conditional statements allow a program to execute different code blocks based on conditions. Python provides three primary types of conditional statements:

  1. if Statement
  2. if-else Statement
  3. if-elif-else Statement

These are used to control the flow of a program based on different conditions.

1. if Statement

The if statement checks a condition and executes the indented block only if the condition evaluates to True.

Syntax:

if condition:
    # Code to execute if the condition is True

Example: Checking if a number is positive

num = 10
if num > 0:
    print("The number is positive")

Output:

The number is positive

🔹 How It Works:

  • The condition num > 0 is evaluated.
  • If it is True, Python executes the indented statement (print() in this case).
  • If it is False, the block is skipped.

Example: Greeting a User

name = input("Enter Name:")
if name == "Alice":
    print("Hello Alice, Good Morning")
print("How are you!!!")

If the user enters "Alice", the program prints "Hello Alice, Good Morning". Otherwise, it only prints "How are you!!!".

2. if-else Statement

The if-else statement is used when we need to execute one block of code if a condition is True and a different block if the condition is False.

Syntax:

if condition:
    # Block executed if condition is True
else:
    # Block executed if condition is False

Example: Checking Even or Odd Number

num = 7
if num % 2 == 0:
    print("Even number")
else:
    print("Odd number")

Output:

Odd number

Example: Greeting Based on User Input

name = input("Enter Name:")
if name == "Alice":
    print("Hello Alice, Good Morning")
else:
    print("Hello Guest, Good Morning")
print("How are you!!!")

If the user enters "Alice", the program prints "Hello Alice, Good Morning". Otherwise, it prints "Hello Guest, Good Morning".

3. if-elif-else Statement

Sometimes, we need to check multiple conditions. The if-elif-else statement is used to handle such scenarios.

Syntax:

if condition1:
    # Executes if condition1 is True
elif condition2:
    # Executes if condition2 is True
elif condition3:
    # Executes if condition3 is True
else:
    # Executes if none of the conditions are True

Example: Assigning Grades Based on Marks

marks = 85
if marks >= 90:
    print("Grade: A")
elif marks >= 75:
    print("Grade: B")
elif marks >= 60:
    print("Grade: C")
else:
    print("Grade: D")

Output:

Grade: B

Example: Choosing a Favorite Brand

brand = input("Enter Your Favourite Brand:")
if brand == "RC":
    print("It is a children's brand")
elif brand == "KF":
    print("It is not that much kick")
elif brand == "FO":
    print("Buy one, get one free")
else:
    print("Other brands are not recommended")

If the user enters "KF", the output will be:

It is not that much kick

4. Short-Hand if-else (Ternary Operator)

Python allows a shorter way to write if-else using a ternary operator.

Syntax:

value_if_true if condition else value_if_false

Example: Checking Voting Eligibility

age = 20
status = "Eligible to vote" if age >= 18 else "Not eligible to vote"
print(status)

Output:

Eligible to vote

5. Nested if Statements

We can place an if statement inside another if statement, known as nesting.

Example: Checking if a Number is Positive and Even

num = 10
if num > 0:
    print("The number is positive")
    if num % 2 == 0:
        print("It is an even number")

Output:

The number is positive
It is an even number

Example: Checking the Largest of Three Numbers

n1 = int(input("Enter First Number:"))
n2 = int(input("Enter Second Number:"))
n3 = int(input("Enter Third Number:"))

if n1 > n2 and n1 > n3:
    print("Biggest Number is:", n1)
elif n2 > n3:
    print("Biggest Number is:", n2)
else:
    print("Biggest Number is:", n3)

If the user enters 10, 20, 30, the output will be:

Biggest Number is: 30

This example shows how multiple if-elif conditions help in decision-making.

6. Important Notes on Conditional Statements

✅ Python Does Not Have a switch Statement

Unlike other programming languages, Python does not provide a switch-case statement. Instead, if-elif-else statements serve the same purpose.

✅ else is Optional

An if statement does not always require an else. If no condition matches and else is absent, nothing happens.

✅ Python Uses Indentation Instead of Braces {}

Python uses whitespace (indentation) to define blocks instead of {} used in languages like C, Java.

❌ Incorrect:

if age >= 18:
print("Eligible to vote")  # Incorrect because it's not indented properly

✅ Correct:

if age >= 18:
    print("Eligible to vote")  # Correct indentation

Conclusion

  • Conditional statements (if, if-else, if-elif-else) help control the flow of execution.
  • The if statement checks a condition and executes a block if True.
  • The if-else statement provides an alternative when the condition is False.
  • The if-elif-else structure helps when multiple conditions need to be checked.
  • Python also supports short-hand if-else (ternary operator) and nested if statements.