Introduction

Conditional statements are used to make decisions in a Python program. They allow the program to execute different blocks of code based on whether a condition is True or False.

Definition

A conditional statement is a control structure that executes a specific block of code only when a given condition is satisfied.

Types of Conditional Statements

Python provides the following conditional statements:

1. if Statement
2. if-else Statement
3. if-elif-else Statement
4. Nested if Statement

1. if Statement

The if statement executes a block of code only if the specified condition is True.

Syntax

if condition:
    # statements

Example

age = 18

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

Output

You are eligible to vote.

2. if-else Statement

The if-else statement executes one block of code if the condition is True and another block if it is False.

Syntax

if condition:
    # True block
else:
    # False block

Example

num = 7

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

Output

Odd Number

3. if-elif-else Statement

The if-elif-else statement is used to check multiple conditions. Once a condition is found to be True, the corresponding block is executed.

Syntax

if condition1:
    # Block 1
elif condition2:
    # Block 2
elif condition3:
    # Block 3
else:
    # Default block

Example

marks = 82

if marks >= 90:
    print("Grade A+")
elif marks >= 80:
    print("Grade A")
elif marks >= 70:
    print("Grade B")
elif marks >= 60:
    print("Grade C")
else:
    print("Fail")

Output

Grade A

4. Nested if Statement

A nested if statement is an if statement placed inside another if statement.

Syntax

if condition1:
    if condition2:
        # statements

Example

age = 20
citizen = True

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

Output

Eligible to vote

Comparison Operators Used in Conditions

Logical Operators

Example

age = 22
has_id = True

if age >= 18 and has_id:
    print("Entry Allowed")
else:
    print("Entry Denied")

Output

Entry Allowed

Flowchart of an if-else Statement

        Start
          |
          v
   Check Condition
      /        \
   True        False
    |             |
Execute IF     Execute ELSE
    |             |
     \           /
          End

Advantages of Conditional Statements

• Enable decision-making in programs.
• Improve program flexibility.
• Handle different situations based on user input.
• Make code more organized and readable.

Applications

Voting eligibility checks

Student grading systems

ATM transactions

Login authentication

Online shopping discounts

Traffic signal control