Syntax and Indentation in Python

Unlike many programming languages that use braces {} or keywords to define code blocks, Python uses indentation as a core part of its syntax. This unique feature makes Python code more readable and consistent, but it also means that proper indentation is not optional — it is mandatory.

In this section, we’ll explore Python’s syntax rules and how indentation defines the structure and flow of a Python program.

1. Python’s Clean Syntax

Python’s syntax is designed to be clear and human-readable. Statements end with newlines rather than semicolons (though semicolons are allowed, they are not recommended). Curly braces {} are not used for grouping code blocks. Instead, Python relies on indentation levels to determine block structure.

Here’s a simple example:

greeting.py

name = "Alice"
print("Hello,", name)

There’s no need to declare variable types (name is automatically recognized as a string), and there are no trailing semicolons.

2. The Role of Indentation

Indentation is not just for readability — it defines the code structure. All statements within the same block of code must be indented the same amount.

A block typically follows structures like if, for, while, def, class, etc.

conditional.py

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

If the indentation is inconsistent or missing, Python will raise an IndentationError.

3. Consistent Use of Spaces or Tabs

You must choose either spaces or tabs for indentation — do not mix them. PEP 8 (Python’s style guide) recommends:

Using 4 spaces per indentation level
Avoiding tabs

Most modern IDEs and code editors are configured to use 4 spaces by default when writing Python code.

4. Nested Indentation

You can nest blocks inside other blocks, just like other languages. Each new block increases the indentation level.

nested_if.py

score = 85
 
if score >= 50:
    print("Pass")
    if score >= 80:
        print("Distinction")

In this example, the inner if block is indented further than the outer block, and Python uses this indentation to determine the scope of each condition.

5. Indentation Errors

Python is strict about indentation. A mismatch in indentation will immediately raise an error.

Example of Incorrect Indentation:

error_example.py

def greet():
print("Hello")  # This will raise an IndentationError

Output:

IndentationError: expected an indented block

To fix it:

corrected_greet.py

def greet():
    print("Hello")

6. Multiline Statements and Indentation

If a statement spans multiple lines, Python allows implicit continuation inside parentheses (), brackets [], or braces {}. You can also use the backslash \ for explicit continuation (though it’s less preferred).

multiline.py

numbers = [
    1, 2, 3,
    4, 5, 6
]

7. Best Practices

Always use 4 spaces for indentation (not tabs).
Configure your editor to display invisible characters (to avoid mixing tabs/spaces).
Keep your indentation consistent within the file.
Avoid deeply nested blocks by using functions where appropriate.

Conclusion

Python’s syntax emphasizes readability and consistency, and indentation is at the heart of its design philosophy. While it may feel strict at first, it promotes clean code and reduces visual clutter, especially in larger projects.

In the next section, we will discuss how to write and use comments in Python to document your code effectively.

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