Nested if-else Statements

In Python, nested if-else statements allow you to embed one or more if-else constructs within another, enabling more complex decision-making processes. This structure is particularly useful when you need to check multiple conditions sequentially.

Basic Syntax:

Python

if condition1:

    # Code to execute if condition1 is True

    if condition2:

        # Code to execute if both condition1 and condition2 are True  

    else:

        # Code to execute if condition1 is True but condition2 is False

else:

    # Code to execute if condition1 is False

Key Points:

• Indentation is crucial to define code blocks within nested if-else statements.

• You can nest if-else statements to any depth, but excessive nesting can make code harder to read and maintain.

• The elif statement can be used as an alternative to nested if statements for multiple conditions.

• Consider using functions to break down complex logic into smaller, reusable units.

Example:

Python

age = 25

nationality = "Canadian"

if age >= 18:

    if nationality == "Canadian":

        print("You are an adult Canadian citizen.")

    else:

        print("You are an adult foreign citizen.")

else:

    print("You are a minor.")

Explanation:

1.    The outer if condition checks if age is greater than or equal to 18.

2.    If the outer condition is true, the inner if checks the nationality.

3.    If both conditions are true, it prints "You are an adult Canadian citizen."

4.    If the outer condition is true but the inner condition is false, it prints "You are an adult foreign citizen."

5.    If the outer condition is false, the else block executes, printing "You are a minor."

Alternative with elif:

Python

if age >= 18 and nationality == "Canadian":

    print("You are an adult Canadian citizen.")

elif age >= 18:

    print("You are an adult foreign citizen.")

else:

    print("You are a minor.")

Best Practices:

• Aim for clear and readable code, even if it means using more variables or functions.

• Avoid excessive nesting as it can reduce code maintainability.

• Consider refactoring complex logic into separate functions.

• Use comments to explain the purpose of nested conditions if necessary.

By understanding and effectively using nested if-else statements, you can create well-structured and flexible Python programs that handle various decision-making scenarios.