06.Conditional_Statements.md

Conditional Statements in Python

(if, if-else, if-elif-else)

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1. Introduction

In programming, we often need to make decisions.

Examples:

• If marks are greater than 40 → Pass
• If age is greater than 18 → Eligible
• If number is even → Print “Even”

To handle such situations, we use conditional statements.

Conditional statements allow the program to execute code based on conditions.

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2. The if Statement

The if statement checks a condition. If the condition is True, the block of code runs.

Syntax:

if condition:
    statement

Example:

age = 20

if age > 18:
    print("Eligible to vote")

If the condition is false, nothing happens.

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3. Indentation (Very Important)

Python uses indentation (spaces) to define blocks.

Correct:

if 5 > 3:
    print("Correct")

Wrong:

if 5 > 3:
print("Correct")   # Error

Always use proper indentation.

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4. The if-else Statement

If the condition is True → first block runs If False → else block runs

Syntax:

if condition:
    statement
else:
    statement

Example:

num = 7

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

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5. The if-elif-else Statement

Used when there are multiple conditions.

Syntax:

if condition1:
    statement
elif condition2:
    statement
else:
    statement

Example:

marks = 75

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

Python checks conditions from top to bottom.

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6. Nested if

An if statement inside another if statement.

Example:

age = 22
citizen = True

if age > 18:
    if citizen:
        print("Eligible to vote")

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7. Using Logical Operators in Conditions

You can combine conditions using:

• and
• or
• not

Example:

age = 20
has_id = True

if age > 18 and has_id:
    print("Entry allowed")

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8. Common Beginner Mistakes

1. Using = instead of ==

if age = 18:   # Wrong

Correct:

if age == 18:

2. Wrong indentation

3. Forgetting colon : after condition

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9. Practice Exercises

1. Take a number and check if it is positive or negative
2. Take marks and print grade
3. Check if a number is divisible by 5
4. Take age and check if eligible to vote

Example:

num = int(input("Enter number: "))

if num > 0:
    print("Positive")
elif num < 0:
    print("Negative")
else:
    print("Zero")

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