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If Conditions

  • Conditional statements allow your Python program to make decisions based on whether a condition is True or False. In this lesson, we focus on the if statement to execute specific code only when a condition is met. You’ll learn the syntax of if, how it controls the flow of execution, and see practical examples.

  • What is a Conditional Statement?

    A conditional statement in Python is used to make decisions in a program.
     It allows the program to execute different blocks of code based on conditions (True or False).

    In simple words:
    “If a condition is true, do this. Otherwise, do something else.”

    Why Do We Use Conditional Statements?

    Conditional statements are used to:

    • Make decisions in programs

    • Control the flow of execution

    • Perform different actions for different inputs

    • Build real-world logic (login systems, grading, validations)

    Without conditions:

    A program runs line by line with no decision-making.

    With conditions:

    A program becomes intelligent and dynamic.

    Real-Life Examples

    Real Life Situation

    Python Condition

    If it rains → take umbrella

    if rain == True

    If marks ≥ 35 → pass

    if marks >= 35

    If age ≥ 18 → vote

    if age >= 18

    If password correct → login

    if password == saved_password

    Types of Conditional Statements in Python

    Python supports the following conditional statements:

    1. if

    2. if-else

    3. if-elif-else

    4. Nested if

    5. Short-hand if

    6. Short-hand if-else (Ternary Operator)

    Basic Syntax of Conditional Statements

    General Syntax

    if condition:

        statement(s)

    Important Rules

    • Condition must return True or False

    • Colon : is mandatory

    • Indentation (spacing) is compulsory in Python

    Key Points to Remember 

    • Conditional statements control program flow

    • Conditions return Boolean values (True / False)

    • Indentation is mandatory in Python

    • elif avoids multiple if statements

    • Short-hand improves readability for simple logic

    Where Conditional Statements Are Used?

    • Login & authentication systems

    • Form validation

    • Grading systems

    • Menu-driven programs

    • Decision-making logic in real applications

  • What is the if Statement in Python?

    The if statement is a decision-making statement in Python.
     It allows a program to execute a block of code only when a specified condition is True.

    If the condition evaluates to False, the code inside the if block is skipped.

    Why Use the if Statement?

    The if statement is used to:

    • Make decisions in a program

    • Compare values using conditions

    • Control the execution flow

    • Implement real-world logic such as eligibility, validation, and access control

    Syntax of if Statement (Detailed)

    Basic Syntax

    if condition:

        statement(s)

    Syntax Explanation

    Part

    Explanation

    if

    Python keyword used for condition checking

    condition

    An expression that returns True or False

    : (colon)

    Indicates the start of the if block

    Indentation

    Defines the code block under if

    statement(s)

    Code executed when condition is True




    Indentation in Python

    Python uses indentation instead of braces {} to define blocks of code.

    Rules:

    • Indentation is mandatory

    • Usually 4 spaces are used

    • All statements under if must have the same indentation level

    Wrong indentation causes an IndentationError

    Using Variables in if Condition

    Variables store values that can be tested using conditions.

Checking Age Eligibility Using if Statement

This program checks whether a person is eligible to vote using an if condition and a variable. 

age = 20

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

  • Explanation

    • age is a variable

    • Condition: age >= 18

    • If condition is True, the message is printed

    Multiple Statements Inside if

    An if block can contain more than one statement.
    All statements must be properly indented.

Executing Multiple Statements Using if Condition

This program executes multiple lines of code when the condition becomes True. 

marks = 75

if marks >= 60:
    print("Result: Pass")
    print("Grade: First Class")
    print("Congratulations!")

  • Explanation

    • Condition: marks >= 60

    • Since the condition is True:

      • All three print statements are executed

    • If condition is False, none of the statements run

    Using Comparison Operators in if

    Common operators used in conditions:

    Operator

    Meaning

    ==

    Equal to

    !=

    Not equal

    >

    Greater than

    <

    Less than

    >=

    Greater than or equal

    <=

    Less than or equal

Comparing Two Numbers Using if Statement

This program compares two numbers using variables and prints a message if the condition is True. 

a = 10
b = 5

if a > b:
    print("a is greater than b")

  • Using Boolean Variables in if

    Boolean variables store True or False.

Checking Login Status Using Boolean Variable

This program checks whether the user is logged in using a Boolean variable. 

is_logged_in = True

if is_logged_in:
    print("Welcome! You are logged in.")

  • Nested Logic (Concept)

    Even inside an if block, Python allows additional logic.

    if condition:

        statement1

        statement2

    All statements execute together when the condition is True.

    Flow of Execution (How Python Works)

    1. Python reads the condition

    2. Condition is evaluated (True or False)

    3. If True → execute indented block

    4. If False → skip the block

    5. Program continues

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