Conditional Statements (if-else)

Conditional statements in Python allow the program to make decisions based on certain conditions. The if, elif, and else statements control the flow of execution by checking whether a condition is True or False.

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1. The if Statement

The if statement is used to execute a block of code if a condition is True.

Syntax

if condition:
    # Code to execute if condition is True

Example

age = 18
if age >= 18:
    print("You are eligible to vote.")  

Output:

You are eligible to vote.

• The condition age >= 18 is True, so the indented block of code is executed.

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2. The if-else Statement

The if-else statement adds an alternative block of code that runs when the condition is False.

Syntax

if condition:
    # Code to execute if condition is True
else:
    # Code to execute if condition is False

Example

age = 16
if age >= 18:
    print("You are eligible to vote.")
else:
    print("You are not eligible to vote.")

Output:

You are not eligible to vote.

• Since age is 16, the if condition is False, so the else block is executed.

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3. The if-elif-else Statement

When multiple conditions need to be checked, elif (short for “else if”) is used.

Syntax

if condition1:
    # Code to execute if condition1 is True
elif condition2:
    # Code to execute if condition2 is True
else:
    # Code to execute if none of the conditions are True

Example

marks = 85

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

Output:

Grade: B

• The first condition marks >= 90 is False.
• The second condition marks >= 75 is True, so "Grade: B" is printed.

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4. Nested if Statements

An if statement can be placed inside another if statement to check multiple conditions.

Syntax

if condition1:
    if condition2:
        # Code to execute if both conditions are True

Example

num = 10

if num > 0:
    print("Positive number")
    if num % 2 == 0:
        print("Even number")

Output:

Positive number
Even number

• The first if condition num > 0 is True, so execution continues inside.
• The nested if condition num % 2 == 0 is also True, so "Even number" is printed.

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5. Short-Hand if and if-else (Ternary Operator)

Single-Line if Statement

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

Output:

x is greater than 5

Single-Line if-else (Ternary Operator)

a = 10
b = 20
min_value = a if a < b else b
print("Minimum value:", min_value)

Output:

Minimum value: 10

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6. Using Logical Operators in if Statements

Logical operators (and, or, not) can be used inside if statements to combine multiple conditions.

Example with and

age = 25
income = 50000

if age > 18 and income > 30000:
    print("Eligible for loan")

Output:

Eligible for loan

• Both conditions are True, so the message is printed.

Example with or

has_passport = True
has_id_card = False

if has_passport or has_id_card:
    print("You can travel")

Output:

You can travel

• Since has_passport is True, the if condition is True.

Example with not

is_raining = False

if not is_raining:
    print("Go outside and enjoy!")

Output:

Go outside and enjoy!

• The not operator reverses False to True, so the block executes.

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7. pass Statement in if Blocks

The pass statement is used as a placeholder when no action is required inside an if block.

Example

num = 10
if num > 5:
    pass  # Placeholder to avoid syntax errors
print("Code continues...")

Output:

Code continues...

• The pass statement prevents an error when an if block has no content.