What is the "if" statement in Python and how to use it?

Question

Jayant Kumar · Accepted Answer

Table of Contants
Introduction:
The if statement in Python is a fundamental control flow structure that allows you to execute specific code blocks based on a condition. By checking whether a condition is True or False, the if statement enables decision-making in your Python programs. Combined with elif (else if) and else, it provides flexibility to handle multiple conditions.
Syntax and Basic Usage of the **if** Statement
The basic structure of an if statement in Python looks like this:
if condition:
    # Code to execute if the condition is True

**condition**: This is an expression that evaluates to either True or False.
Code block: Indented lines of code that will execute only if the condition is True.

Example:
age = 18

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

In this example, if the age is greater than or equal to 18, the message "You are eligible to vote." is printed.

How the if Statement Works

The condition is evaluated.
If the condition is True, the code inside the if block is executed.
If the condition is False, the code inside the if block is skipped.

Using else for an Alternative Condition
The else statement provides an alternative block of code that executes when the if condition is False.
Syntax:
if condition:
    # Code to execute if the condition is True
else:
    # Code to execute if the condition is False

Example:
age = 16

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

If the age is less than 18, the message "You are not eligible to vote." is printed.

Adding Multiple Conditions with elif
The elif (else if) keyword allows you to check additional conditions when the initial if condition is False. You can chain multiple elif statements together to handle different scenarios.
Syntax:
if condition1:
    # Code to execute if condition1 is True
elif condition2:
    # Code to execute if condition2 is True
else:
    # Code to execute if all conditions are False

Example:
score = 85

if score >= 90:
    print("Grade: A")
elif score >= 80:
    print("Grade: B")
elif score >= 70:
    print("Grade: C")
else:
    print("Grade: D")

In this case, if the score is between 80 and 89, the message "Grade: B" is printed.

Nested if Statements
You can place an if statement inside another if statement to check multiple conditions in a hierarchical way. This is called nesting.
Example:
age = 20
has_id = True

if age >= 18:
    if has_id:
        print("You are allowed to enter.")
    else:
        print("You need an ID to enter.")
else:
    print("You are not old enough to enter.")

In this example, if the age is greater than or equal to 18 and the person has an ID, they are allowed to enter.

Using if Statements with Logical Operators
You can use logical operators like and, or, and not to combine multiple conditions in a single if statement.
Example:
age = 25
has_ticket = True

if age >= 18 and has_ticket:
    print("You can watch the movie.")
else:
    print("You cannot watch the movie.")

Here, both conditions (age >= 18 and has_ticket) must be True for the message "You can watch the movie." to be printed.

Practical Examples of Using if Statements
1. Simple Decision Making:
temperature = 30

if temperature > 25:
    print("It's hot outside.")
else:
    print("It's cool outside.")

2. Using Multiple Conditions:
number = 15

if number % 2 == 0:
    print("The number is even.")
else:
    print("The number is odd.")

3. Checking Membership in Lists:
fruits = ["apple", "banana", "cherry"]

if "apple" in fruits:
    print("Apple is in the list.")
else:
    print("Apple is not in the list.")

4. Handling User Input:
user_input = input("Enter your age: ")

if int(user_input) >= 18:
    print("You are an adult.")
else:
    print("You are a minor.")

Conclusion:
The if statement in Python is essential for controlling the flow of your programs by making decisions based on conditions. Whether you need to check one condition, multiple conditions with elif, or handle alternative scenarios with else, the if statement provides the foundation for decision-making in Python. By combining it with logical operators and nesting, you can build complex and flexible control structures to make your code smarter and more dynamic.

What is the "if" statement in Python and how to use it?

Table of Contants

Introduction:

Example:

How the `if` Statement Works

Using `else` for an Alternative Condition

Syntax:

Example:

Adding Multiple Conditions with `elif`

Syntax:

Example:

Nested `if` Statements

Example:

Using `if` Statements with Logical Operators

Example:

Practical Examples of Using `if` Statements

1. Simple Decision Making:

2. Using Multiple Conditions:

3. Checking Membership in Lists:

4. Handling User Input:

Conclusion:

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