Python Conditional Statements

What are Conditional Statements?

In real life, we make decisions all the time:

• If it’s raining, take an umbrella.
• If you're hungry, eat something.
• Otherwise, continue your day.

Python also lets us make decisions in our code using conditional statements.

In Python, for conditional statements, we use:

• if – is used check a condition
• elif – is used to check another condition if the first one was false
• else – is used to do specific operations if nothing above is true

1. if Statement

The if statement is used to run a block of code only when a given condition is True.

Syntax

if condition:
    # code to run if condition is True

• if: The keyword that starts the conditional statement.
• condition: An expression that evaluates to either True or False.
• The colon : marks the start of the indented code block.
• Indented block: Code that will execute only if the condition is true.

Example

x = 10

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

x is greater than 5

Check if x > 5 (Python)

The variable x holds the value 10. When Python checks the condition x > 5, it evaluates to True. As a result, the print() statement inside the if block is executed, and the message is shown in the output.

Flowchart

2. if-else Statement

The if-else statement allows you to define an alternate block of code to run when the condition is False. It provides a clear choice between two paths.

Syntax

if condition:
    # code to run if condition is True
else:
    # code to run if condition is False

Syntax Explanation

• if: Starts the conditional check.
• condition: An expression that returns True or False.
• :: A colon follows the condition and begins the indented block.
• Indented block (under if): Executes if the condition is True.
• else:: Specifies the alternate block to run if the condition is False.
• Indented block (under else): Executes if the condition is False.

Example

age = 16

if age >= 18:
    print("You can vote.")
else:
    print("You cannot vote.")

You cannot vote.

Voting Eligibility (Python)

Explanation: The variable age is assigned the value 16. Python checks the condition age >= 18, which evaluates to False. Therefore, the code inside the else block runs and prints You cannot vote..

3. if-elif-else Ladder

Use the if-elif-else structure when you want to test multiple conditions in sequence. Python evaluates each condition in order and executes the block under the first True condition.

Syntax

if condition1:
    # code block 1
elif condition2:
    # code block 2
elif condition3:
    # code block 3
else:
    # default code block if none above are true

Syntax Explanation

• if: Checks the first condition. If it’s True, its block is executed and the rest are skipped.
• elif: Stands for “else if.” It lets you check more conditions if the previous ones are False.
• else: A fallback that runs if none of the if or elif conditions are true.
• Only the first block with a True condition runs; the rest are ignored.

Example

marks = 75

if marks >= 90:
    print("Grade: A")
elif marks >= 70:
    print("Grade: B")
elif marks >= 50:
    print("Grade: C")
else:
    print("Grade: F")

Grade: B

Grade Based on Marks (Python)

Explanation: The value of marks is 75. The first condition (marks >= 90) is false, so Python checks the next one: marks >= 70. This is true, so it prints Grade: B. The rest of the conditions are skipped.

4. Nested if Statements

You can also put one if inside another. This is called nesting.

num = 10

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

Positive even number

Nested If: Positive Even Check (Python)

Why? First, num > 0 is true. Then, 10 % 2 == 0 (means even), so the inner print runs.

Important Notes When Using Conditional Statements

• Use colons (:) after if, elif, and else.
• Indent the code block under each condition using spaces (usually 4).
• Conditions are usually comparisons: ==, !=, >, <, >=, <=.