11 Indentation

Before we explore Python functions in the next section, it’s crucial to understand Python’s indentation rules, as they are fundamental to writing structured and error-free Python code.

Indentation is not just a matter of style in Python; it is syntactically significant. Python uses indentation to define blocks of code. The correct use of indentation is essential for your code to run as expected.

Key Points About Indentation:

Consistency: Python’s standard is to use 4 spaces per indentation level, though some environments may configure tabs to automatically convert to spaces.
Blocks of Code: Functions, loops, conditionals, and other control structures rely on indentation to define what code belongs inside the block.

11.1 Proper Indentation

Example code:

def compute_area(width, height):
    # This is the start of a function block
    area = width * height 
    return area 

# Calling the function
print(compute_area(5, 10))  # This line is not indented, showing it's not part of the function

Explanation:

The function compute_area starts with a colon (:) and the subsequent code is indented four spaces.
Both the calculation of area and the return statement are part of the function due to their indentation.
The print statement is not indented relative to the function definition, indicating it is outside the function.

Certainly! Here’s an example that illustrates incorrect indentation and the potential issues it can cause. This example can be included in the introductory section on Python indentation to show the importance of following Python’s indentation rules accurately.

11.2 Incorrect Indentation

Example code with incorrect Indentation:

def calculate_percentage(total, amount):

    if total > 0:
    percentage = (amount / total) * 100 
    return percentage  
else:
    return 0

IndentationError: expected an indented block after 'if' statement on line 3

Explanation:

Error: The example above will result in a IndentationError because the indentation levels are not consistent.
Line 3: The line percentage = (amount / total) * 100 is meant to be executed if the condition total > 0 is true. However, it’s not indented, making it unclear whether it’s supposed to be inside the if statement or outside.
Line 4 and 5: The return percentage statement should be indented to align under the if condition, indicating that it is part of the if block. The else: line is also not correctly aligned with the if, causing a syntax error.

Corrected Version:

def calculate_percentage(total, amount):
    if total > 0:
        percentage = (amount / total) * 100  
        return percentage  
    else:
        return 0

What this corrects:

The percentage = (amount / total) * 100 statement is now properly indented under the if condition, clearly indicating it belongs to the block that executes when total > 0.
The return percentage is also indented correctly to show that it’s part of the if condition. The else block is aligned with the if statement, maintaining consistent structure.

This example highlights how improper indentation can lead to syntax errors and logical errors in Python. It’s vital to keep a consistent indentation level throughout the code block to ensure clarity and functionality of the code. By adhering to these practices, you prevent runtime errors and make your code easier to read and debug.