Python if-else Statement

The if-else statement in Python is used to execute a block of code if a condition is true, and a different block of code if the condition is false.

Syntax:

if condition:
   # Block of code if condition is True
else:
   # Block of code if condition is False

Indentation is important in Python. All code inside the if or else block should be properly indented.

Example 1: Basic if-else

age = 20
if age >= 18:
   print("You are an adult.")
else:
   print("You are not an adult.")

Output:

You are an adult.

Example 2: Odd or Even

number = 7
if number % 2 == 0:
   print("The number is even.")
else:
   print("The number is odd.")

Output:

The number is odd.

Example 3: Using Input

score = int(input("Enter your score: "))
if score >= 50:
   print("You passed the test.")
else:
   print("You failed the test.")

Sample Output (user enters 65):

You passed the test.

When to Use if-else

  • Checking conditions and responding with two different outcomes.
  • Making binary decisions (yes/no, true/false).
  • Validation logic in applications.

Important Notes:

  • Python uses colons (:) after if and else.
  • The else block is optional, but often used for fallback logic.

Flowchart

See the corrected flowchart representation of the if-else logic:

  • If condition is true → execute block 1
  • If condition is false → execute block 2
  • Both paths lead to the end

Practice Exercise:

Write a program to check if a number is positive or negative.

num = -5
if num >= 0:
   print("Positive number")
else:
   print("Negative number")

Output:

Negative number