What is Indentation in Python Programming? Examples, Rules, Pros & Cons, Full Guide

Indentation is an important and fundamental aspect of Python programming. Indentation in other languages, such as C, C++, Java, etc., is for the sake of readability. However, Python indentation is mandatory and an essential practice that must be followed while writing code. 

You might ask, what will happen If we don’t abide by an indentation in Python? Well, this article will walk you through all the aspects involved in it. 

Here, we will be focusing on: 

• What is Python Indentation with an example?

• Is indentation required in Python?

• Why indentation is important in Python?

• What is the role of indentation in Python?

… and also throw some light on how to write readable code in Python.

As part of our Python Tutorial for Beginners, we have so far talked about:

• What is Python?

• Benefits of Python

• Uses and applications of Python

• Python keywords

• Python installation process

So, you would like to check those write-ups out to understand the basics first.

Let’s begin by understanding what is Python indentation.

In simple terms, an indentation in Python refers to the spaces placed at the beginning of the code lines. Its primary importance is that it treats statements with the same indentation level, i.e., statements with an equal number of whitespaces before them, as a single piece of block. 

The same indentation level is treated as one scope in Python. Indentation serves as a means of signaling to the Python interpreter that a group of statements belong to a particular block of code.

Similar to how brackets are an integral part of other programming languages, Indentation is a mandatory aspect in Python. We will discuss the importance of indentation more once we get to the advantages section of it. Before that let’s closely understand what is indentation in Python with examples.

Below examples will help you understand the concept of Indention better along with conditional statements.

Demo: 

1. Statement:               Code block 1 statement begins

2. if condition:              Code block 1 condition continues

3. if condition:              Code block 2 statement begins

     4. Statement —--->      Code block 3 stmt begins

     5. else:                           Code block 2 statement cont.

     6. Statement:                 Code block 3 continues

     7. Statement:                 Code block 1 continues

Let’s try to decrypt what is happening here.

• We know the basics of indentation, so all statements which are on the same level of Indentation belong to a single block. From the above scenario, we can infer that statements in line number 1, 2, and 7 belong to code block 1 and have zero or the lowest level of indentation. Statements 3 and 5 are indented one step ahead, which forms another block with the first level of indentation. Likewise, statements 4 and 6 form a code block number 3, forming a second level of indentation.

• In this way, you can analyze and define blocks and see which statements belong to those blocks. 

Now let’s see the execution part of it:

• Code execution begins at line 1 followed by checking the if condition at line 2; If the evaluation of the condition returns true, then control goes inside of the if block. 

• If line 3 returns true, the flow enters into executing the statement in line 4. If the evaluation of line 3 returns false, then the control goes into the execution of statement 6.

• If the second line itself returns false, then statement 7 would have been executed. 

This is how we indent the python code for successful execution.

Now that we have a clear understanding of how a code block is indented in Python and how those code blocks execute, let’s dive into some real examples of indentation in Python Programming Language:

Example 1

Let’s see if a number is odd or even and if it’s zero return zero.

Program:

x = 10;

if x != 0:

  if x%2 == 0:

    print("The number is even")

  else:

    print("The number is odd")

else:

  print("The number is zero, i.e., it is neither even nor odd")

Output:

The number is even

Since the variable x is not zero, it satisfies the first condition check and enters the first code block. For the next condition check, x should either be even or odd, according to the example, x is even, so the second condition is also satisfied, now it’ll enter the second code block. As both the conditions are true, it will print, ”The number is even”. 

In this program, the statements that are inside the bodies of if and else are indented.

Example 2

Let’s see a while condition:

Program: 

i = 3

while(i <= 6):

    print("Value is " + str(i))

    i = i + 1

Output:

Value is 3

Value is 4

Value is 5

Value is 6

The value of i is initialized to 3, while block forms one block of code. Now i is less than 6 and it satisfies our condition check, so the next indented statements will execute. Here the statements “Value is ” + str(i) and i = i + 1, are uniformly indented to form a block and are also the body of the statement.

We have observed from the above examples how the indentation works and how it forms a block of code.

Let’s examine the output if we do not pay attention to indentation:

Program:

if 5 > 2:

print("Five is greater than two!")

Output:

Traceback (most recent call last):

  File "/usr/lib/python3.8/py_compile.py", line 144, in compile

    code = loader.source_to_code(source_bytes, dfile or file,

  File "", line 846, in source_to_code

  File "", line 219, in _call_with_frames_removed

  File "./prog.py", line 2

    print("Five is greater than two!")

    ^

IndentationError: expected an indented block

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

  File "", line 1, in

  File "/usr/lib/python3.8/py_compile.py", line 150, in compile

    raise py_exc

py_compile.PyCompileError: Sorry: IndentationError: expected an indented block (prog.py, line 2)

You will get an IndentationError because the Python interpreter cannot interpret the code which will result in an unsuccessful compilation.

The correct way of writing the program is shown below:

Correct program:

if 5 > 2:

   print("Five is greater than two!")

Correct Output:

Five is greater than two!

In the Python Programming Language, adhering to indentation is a requirement that cannot be overlooked. Here are some of the main rules of Python indentation:

• Indentation cannot be used on the very first line of the Python code.

• The standard indentation level in Python is four spaces. This indicates that each level of indentation should be of four spaces.

• Do not mix tabs and spaces when indenting code in Python. It is recommended to use only spaces as this ensures consistency across different text editors and IDEs. To avoid confusion, always use spaces on all the platforms. 

• Consistency is important while indenting code in Python. All the lines that come under a code block should be indented at the same level.

• Indentation is an important part of the Python programming language, however, it should be used in moderation and not be overused. Always avoid extra indentation, as it will make the code harder to read and understand.

• Indentation is not optional. It is mandatory in Python, not adhering to it can cause errors.

If you are preparing for a new job, you must check out the top Python interview questions and answers.

Let’s begin by starting on the right foot and examine the benefits of using Indentation in Python Programming Language:

1. Improves Code Readability

From the above examples, we can infer that Indentation in Python makes the code more readable by clearly indicating code blocks and making it easy for developers to understand the flow of the program and locate specific sections of code. 

2. Enforces Structure

No doubt, Indentation provides a structure to Python code. Indentation makes it clear where the code blocks start and end. Structuring is important when it comes to the complex and large codebase, as it makes it easier to avoid naming conflicts and other issues. It also helps in maintaining and understanding the code better.

Well-structured code is more maintainable. This can prolong the life of the code base and can make it more valuable over a period of time.

3. Facilitates Debugging

Indentation makes the code clearly visible and properly structured. This can help developers quickly locate and fix errors in the code. 

For example, if a developer is trying to locate an error in a code block, indentation makes it easy to identify the specific code block in question and locate the lines of code that are causing the error. This in turn saves a lot of time, as the developer does not have to search for the entire codebase to find the problem. 

If there are debugging issues related to variable scope or function calls, an indentation can be effectively used to indicate the scope of variables and functions.

4. Improves Code Reusability

Well-structured and indented code is easier to reuse and modify for different projects, as it is more readable and understandable. Indentation saves a lot of developers’ time as they don’t need to rewrite the same code from scratch.

Additionally, well-structured and indented code is easier to modify and adapt to new requirements. When a developer can understand the code easily, he or she can make changes with more confidence, knowing that he or she is not going to break any functionality. 

5. Enhances Code Maintainability

Indentation makes it easier to locate errors and bugs in the code, as well as making it easier to update and modify the code in the future. In order to have a better idea of everything related to this programming language, you must regularly practice Python quiz online.

Now that we have covered the positive aspects, let’s delve into the negative aspects of using Indentation in Python Programming Language:

1. Inconsistency can lead to errors

If different parts of the code block are indented differently, it can lead to confusion and errors. This will cause a huge problem, especially when working on a large project with a complex code base.

2. Requires Strict adherence

Developers cannot move forward if they don’t follow indentation religiously. It is a strict requirement of the Python programming language.

3. Extra effort

Developers might take indentation as an extra effort in order to maintain consistency throughout the project. 

4. Does not improve performance

You might believe that since we have discussed the importance of indentation, it could also have an impact on performance. However, an indentation in Python has no role to play when it comes to the performance of the code.

Indentation can be confusing for some and may seem limiting, but with the help of Python Indentation Checker, we can overcome these challenges. Python Indentation Checker? What is that?

It is a tool that checks for the indentation of Python code to ensure it is consistent and follows the proper convention. This tool can help to identify and fix errors in the code, such as indentation issues or inconsistent use of tabs and spaces. Some of the famous Python indentation tools are PEP8, Black, autopep8, etc. 

You can use Python Online Compiler to run a code or program.

Let’s look at some of the features of the Python indentation checker tools:

1. Detects Indentation errors

The tool can directly detect all the indentation errors such as unexpected indentation levels, inconsistent use of spaces and tabs, and missing indentation. 

2. Integration with text editors and IDEs

The tool can be easily integrated with popular text editors and IDEs of your choice.

3. Reports and Visualization

The tool can generate reports and visualizations to show all the indentation error history found in the code. This makes the developer's life a little easy!  

4. Auto-fixing capability

You don’t have to do anything, this tool can automatically fix the indentation in Python code.

5. Configurable rules

The tool can also be configured to check for specific indentation rules and conventions.

Below are some commonly asked questions about Python indentation along with their answers:

1. What is indentation in Python with an example?

In Python, indentation plays a crucial role in defining the structure and scope of the code. It is used to indicate blocks of code that belong together, such as the body of a for loop or an if statement. The amount of indentation is usually represented by four spaces, although tabs can also be used, as long as the same number of spaces are used consistently throughout the code.

For example, consider the following code:

x = 10

if x > 5:

    print("x is greater than 5")

    x = x + 1

    print("x is now", x)

In this example, the two lines of code indented under the if statement belong to the block of code executed when the condition x > 5 is true. The amount of indentation indicates that these two lines of code should be executed together, as part of the same block.

2. Why is indentation important in Python?

Indentation is important in Python because it is used to define the scope of code blocks. Python uses indentation to determine where a code block starts and ends, and it is a crucial part of the language syntax.

3. What is an indent block in Python?

In Python, an indent block refers to a group of one or more lines of code that are indented at the same level. Indent blocks are used to define the structure and scope of the code, and they are used to group related lines of code together.

4. How many spaces to use for indentation in Python?

The Python Style Guide recommends using 4 spaces for indentation. However, some developers may use 2 spaces or a tab, but it is important to be consistent within a single project.

5. What happens if I forget to indent a line in Python?

If you forget to indent a line in Python, you may get a syntax error. Indentation is a crucial part of the syntax in Python, and forgetting to indent a line can cause the code to not run as expected.

6. Can I use a tab for indentation in Python?

Yes, you can use a tab for indentation in Python, but it is recommended to use 4 spaces for indentation. Some developers prefer to use tabs for indentation because it saves space, but it is important to be consistent within a single project.

7. Can I mix tabs and spaces for indentation in Python?

No, it is not recommended to mix tabs and spaces for indentation in Python. It is best to be consistent with your indentation style and use either tabs or spaces throughout your code.

8. Is indentation required in Python?

Yes, indentation is mandatory in Python. Indentation is a crucial part of the syntax in Python, and it is used to define the scope of code blocks and improve the readability of the code.

9. How does Python handle indentation in multi-line statements?

In Python, multi-line statements can be broken down into multiple lines using parentheses, brackets, or backslashes. The indentation for the continuation lines should align with the first non-whitespace character after the opening parenthesis or bracket.

10. Which are the best Python indentation checker tools online?

There are several online tools available for checking the indentation of Python code. Here are some of the best ones:

• PyLint: 

PyLint is a popular tool for checking the quality and consistency of Python code. It checks for a variety of issues, including indentation errors, and provides detailed feedback to help improve the code.

• Flake8: 

Flake8 is a Python linting tool that checks for style, formatting, and syntax issues in Python code, including indentation problems.

• PEP8 Online: 

PEP8 Online is a simple tool that checks Python code against the PEP 8 style guide, which includes recommendations for proper indentation.

• PythonTutor: 

PythonTutor is an online tool that helps people learn and understand Python code by visualizing the execution of the code. It can also be used to check for indentation errors, among other things.

• Repl.it: 

Repl.it is an online development environment that supports a variety of programming languages, including Python. It has a built-in linter that checks for indentation errors, among other things.

These are just a few of the many online tools available for checking Python indentation. It's important to find the tool that works best for you and your needs, whether that's a simple online tool or a more sophisticated code analysis tool like PyLint or Flake8.

11. What is an unexpected indent in Python?

"Unexpected indent" is an error message in Python that occurs when the indentation of a line of code is incorrect. In Python, indentation is used to define the structure and scope of the code, and each level of indentation must be consistent throughout the code. If a line of code is indented too much or too little, it can cause a "Unexpected indent" error.

For example, consider the following code:

x = 10

if x > 5:

    print("x is greater than 5")

  print("This line is indented too little")

In this example, the line print("This line is indented too little") would cause an "Unexpected indent" error, because it is indented less than the line above it. This indicates that it is not part of the same block of code, which can lead to unexpected behavior.

To fix this error, make sure that each line of code is indented the same amount within a block of code, and that the amount of indentation is consistent throughout the code.

If you get stuck with indentations now, you know where to go!

With this, we conclude that in this article, we aimed to demonstrate the importance of Indentation in Python Programming. Though it may seem small, those four spaces can significantly impact the execution and success of your Python code. We hope this article provided valuable insights and new knowledge for you!