How to Use Python If Statement

Python

Introduction

The Python if statement is a fundamental control structure that you can use to make decisions in your code. The statement allows you to execute specific blocks of code only when certain conditions are met. This is useful for handling different scenarios, validating inputs, and controlling program flow. By using if statements, you can write more dynamic and responsive programs.

This guide shows you how to use the Python if statement effectively.

Prerequisites

Before you begin:

  • Deploy a VPS server. For instance, Ubuntu 24.04.
  • Create a non-root sudo user.
  • Install Python.

Declare Python if Statement

The if statement in Python evaluates a condition and executes a block of code if the condition is true. The syntax is straightforward and easy to understand. Here's an example:

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

The above example evalulates the x > 5 condition. If it is true, the code inside the if block runs, printing x is greater than 5.

Certainly! Here's the extended markdown with additional examples for or and not:

Combine Multiple Conditions

You can combine multiple conditions in a single if statement using logical operators like and, or, and not. These operators allow you to create more complex conditions.

  • Use and to check if all conditions are true.
  • Use or to check if at least one condition is true.
  • Use not to negate a condition.

Use and with if Statement

All conditions must be true.

Python
age = 25
income = 50000

if age > 18 and income > 30000:
    print("You are eligible for a loan.")

In the above example, both conditions (age > 18 and income > 30000) must be true in order for Python to print the message.

Use or with if Statement

At least one condition must be true.

Python
age = 16
income = 70000

if age > 18 or income > 30000:
    print("You are eligible for a partial loan.")

In this case, although age > 18 is false, income > 30000 is true. Since one condition is true, Python prints the message.

Python
has_job = False
has_savings = True

if has_job or has_savings:
    print("You have financial stability.")

Here, as has_savings is true, Python prints the message even if has_job is false.

Use not with if Statement

Negate a condition.

Python
is_student = True

if not is_student:
    print("You are not a student.")
else:
    print("Welcome, student!")

In the above code case, not is_student evaluates to false because is_student is true. The program will print the message from the else block.

Python
temperature = 35

if not temperature < 30:
    print("It's hot outside!")

Here, not temperature < 30 evaluates to true because temperature < 30 is false, so the message will be printed.

Combine or and not for Advanced Condition

Python
age = 30
is_married = False

if age > 25 or not is_married:
    print("You qualify for the survey.")

In this case, age > 25 is true, so Python prints the message regardless of the second condition.

Using Nested if Statements

Nested if statements allow you to check for additional conditions within an existing if block. This approach is useful when you need to make more granular decisions based on multiple criteria.

  • Start with an outer if statement.
  • Add an inner if statement inside the outer block.
  • Ensure proper indentation to maintain the structure.

Here's an example:

Python
num = 15

if num > 10:

    print("Number is greater than 10")

    if num > 20:
        print("Number is also greater than 20")
    else:
        print("But not greater than 20")

In the above example, the outer if checks if num is greater than 10. If true, the outer if prints a message and then checks if num is also greater than 20.

Implement Python if Statement Best Practices

To write clean and efficient if statements, follow these best practices:

  • Keep conditions simple and readable.
  • Avoid deeply nested if statements by using elif or breaking code into functions.
  • Use meaningful variable names to make conditions clear.
  • Test all possible conditions to ensure your code handles every scenario.

Here's an example of using elif:

Python
score = 85

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

This structure is easier to read and maintain than multiple nested if statements.

Discover if Statement Practical Use Cases

The if statement is versatile and can be used in various scenarios:

  • Validating user input to ensure it meets specific criteria.
  • Controlling program flow based on dynamic conditions.
  • Filtering data by applying conditions to datasets.
  • Implementing business logic, such as discounts or eligibility checks.

Here's an example of validating user input:

Python
user_age = int(input("Enter your age: "))

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

This ensures the program responds appropriately based on the user's age.

Conclusion

The Python if statement is a powerful tool for making decisions in your code. It allows you to execute specific blocks of code based on conditions, making your programs more dynamic and responsive. By combining conditions, nesting if statements, and following best practices, you can write clean and efficient code. Whether you're validating inputs, controlling program flow, or implementing business logic, the if statement is essential in coding applications.