IndentationError in Python — How to Fix (2026) | Tutorials Logic

What is This Error?

The IndentationError is one of the most common Python errors for beginners. It occurs when Python encounters incorrect or inconsistent indentation in your code. Unlike most programming languages that use braces {} for code blocks, Python uses indentation to define code structure.

Error Message:
IndentationError: expected an indented block
IndentationError: unexpected indent
IndentationError: unindent does not match any outer indentation level

Common Causes

Missing indentation after colon (:) in if, for, while, def, class statements
Mixing tabs and spaces for indentation
Inconsistent indentation levels (2 spaces vs 4 spaces)
Extra or unexpected indentation
Copy-pasting code with different indentation styles

Quick Fix (TL;DR)

Quick Solution

# ❌ Problem
if x > 5:
print("Greater")  # Missing indentation!

# ✅ Solution: Add proper indentation (4 spaces recommended)
if x > 5:
    print("Greater")

# ✅ Configure your editor:
# - Use 4 spaces per indentation level
# - Convert tabs to spaces
# - Enable "show whitespace" to see indentation

Common Scenarios & Solutions

Scenario 1: Missing Indentation After Colon

The most common cause - forgetting to indent code after statements that require a code block.

Problem

def greet(name):
print(f"Hello, {name}")  # IndentationError!

if age >= 18:
print("Adult")  # IndentationError!

for i in range(5):
print(i)  # IndentationError!

Solution

def greet(name):
    print(f"Hello, {name}")  # Properly indented

if age >= 18:
    print("Adult")  # Properly indented

for i in range(5):
    print(i)  # Properly indented

Scenario 2: Mixing Tabs and Spaces

Python 3 doesn't allow mixing tabs and spaces. This often happens when copying code from different sources.

Problem

def calculate():
    x = 10  # 4 spaces
	y = 20  # Tab character - IndentationError!
    return x + y

Solution

def calculate():
    x = 10  # 4 spaces
    y = 20  # 4 spaces (consistent)
    return x + y

# Configure your editor to convert tabs to spaces
# VS Code: "editor.insertSpaces": true
# PyCharm: Settings → Editor → Code Style → Python → Use tab character: unchecked

Scenario 3: Inconsistent Indentation Levels

Using different numbers of spaces for indentation at the same level causes this error.

Problem

def process_data():
    if True:
        print("Start")  # 4 spaces
      print("Middle")  # 2 spaces - IndentationError!
        print("End")    # 4 spaces

Solution

def process_data():
    if True:
        print("Start")  # 4 spaces
        print("Middle")  # 4 spaces (consistent)
        print("End")    # 4 spaces

Scenario 4: Unexpected Indent

Adding indentation where it's not expected, usually at the start of a file or after a complete statement.

Problem

    print("Hello")  # Unexpected indent at file start!

x = 10
    y = 20  # Unexpected indent after complete statement!

Solution

print("Hello")  # No indentation at file start

x = 10
y = 20  # Same indentation level

Scenario 5: Empty Code Block

Python requires at least one statement in every code block. Use pass for empty blocks.

Problem

def todo_function():
    # Will implement later
# IndentationError: expected an indented block

if condition:
# IndentationError!

Solution

def todo_function():
    # Will implement later
    pass  # Use pass for empty blocks

if condition:
    pass  # Placeholder

# Or use ellipsis (Python 3+)
def another_function():
    ...  # Also valid for empty blocks

Best Practices to Avoid This Error

Use 4 spaces per indentation level - PEP 8 standard for Python code
Never mix tabs and spaces - Configure your editor to convert tabs to spaces
Enable "show whitespace" in your editor - Makes indentation visible
Use a Python-aware editor - VS Code, PyCharm, or Sublime with Python plugins
Run python -tt script.py - Detects tab/space mixing issues
Use autopep8 or black - Auto-format your code to fix indentation
Be consistent - Stick to one indentation style throughout your project

Related Errors

Key Takeaways

IndentationError occurs when Python encounters incorrect or inconsistent indentation
Python uses indentation (not braces) to define code blocks
Use 4 spaces per indentation level as per PEP 8 standard
Never mix tabs and spaces - configure your editor to use spaces only
Every statement ending with colon (:) requires an indented block below it
Use pass or ... for empty code blocks that you'll implement later