Python if-else Condition

if-else statements let your program make decisions — it executes different blocks of code based on whether a condition is true or false.

Basic Syntax

if condition:
    # code block if condition is True
else:
    # code block if condition is False

• The condition is an expression that evaluates to True or False.
• The indented code under if runs only when the condition is True.
• The indented code under else runs if the condition is False.

Example 1: Simple if-else

age = 20

if age >= 18:
    print("You are an adult.")
else:
    print("You are a minor.")

Output:

You are an adult.

Explanation:

• If age is 18 or more, it prints "You are an adult."
• Otherwise (if age is less than 18), it prints "You are a minor."

Example 2: if-elif-else Ladder

When you have multiple conditions, use elif (short for "else if"):

marks = 75

if marks >= 90:
    print("Grade: A")
elif marks >= 75:
    print("Grade: B")
elif marks >= 50:
    print("Grade: C")
else:
    print("Grade: F")

Output:

Grade: B

Explanation:

• Checks conditions from top to bottom.
• Once a true condition is found, the corresponding block runs, and the rest are skipped.
• Here, marks >= 75 is true, so it prints "Grade: B".

Key Points:

• The else block is optional.
• Python requires a colon : after if, elif, and else.
• Code blocks under each condition must be indented (typically 4 spaces).
• Conditions can be any expression that returns True or False.

Example 3: Using Logical Operators in Conditions

temperature = 25

if temperature > 30:
    print("It's hot outside.")
elif temperature >= 20 and temperature <= 30:
    print("The weather is pleasant.")
else:
    print("It's cold outside.")

Output:

The weather is pleasant.

Summary

• Use if to test a condition.
• Use elif for additional checks.
• Use else for the default case.
• Always indent the code inside these blocks.
• Use comparison operators (==, !=, >, <, >=, <=) to form conditions.
• Combine conditions with logical operators (and, or, not).