IndentationError: Expected an Indented Block - Python's Annoying Error

**IndentationError: expected an indented block**

Python's most annoying error. Especially for beginners.

Why Python Cares About Spaces

Other languages use braces: ```javascript if (true) { console.log('yes'); } ```

Python uses indentation: ```python if True: print('yes') ```

No indentation = error.

Common Mistakes

**1. No indentation after colon** ```python def hello(): print('hi') # Error: expected indent ```

**Fix:** ```python def hello(): print('hi') ```

**2. Mixing tabs and spaces** ```python def hello(): print('hi') # spaces print('bye') # tab - looks same but isn't ```

Python sees these as different. Error.

**Fix:** Use only spaces. Set your editor to convert tabs to spaces.

**3. Wrong amount of spaces** ```python if True: print('1') # 2 spaces print('2') # 4 spaces - Error ```

Be consistent. Use 4 spaces (PEP 8 standard).

**4. Empty function/class** ```python def process(): # will add later

next_function() # Error: process is empty ```

**Fix with pass:** ```python def process(): pass # placeholder ```

VS Code Settings

Add to settings.json: ```json { "editor.tabSize": 4, "editor.insertSpaces": true, "editor.detectIndentation": false } ```

Tab key now inserts 4 spaces.

PyCharm Settings

Settings → Editor → Code Style → Python → Tabs and Indents - Tab size: 4 - Indent: 4 - Use tab character: unchecked

Find Mixed Indentation

Run: ```bash python -m tabnanny yourfile.py ```

Shows where tabs and spaces are mixed.

The Copy-Paste Problem

Copied code from web has weird indentation?

**Quick fix in VS Code:** 1. Select all code 2. Shift + Tab (removes all indentation) 3. Select code blocks 4. Tab (re-indent properly)

Or use auto-format: - Windows/Linux: Shift + Alt + F - Mac: Shift + Option + F

Real Example

I copied code from Stack Overflow: ```python def calculate(x, y): if x > y: return x - y else: return y - x ```

Looked fine. Got IndentationError. Why?

Web used tabs. My editor expected spaces.

**Solution:** ```bash cat -A yourfile.py ```

Shows tabs as ^I. Delete and re-type with spaces.

The Invisible Space

Sometimes you have weird Unicode spaces. Look normal but Python hates them.

Check: ```python # your code here ```

If error on a line that looks fine, delete all spaces on that line and re-add them.

Multi-line Statements

Be careful with backslash: ```python total = 1 + 2 + \ 3 + 4 # must align properly ```

Better use parentheses: ```python total = (1 + 2 + 3 + 4) ```

No backslash needed.

Lists and Dicts

This is fine: ```python my_list = [ 'item1', 'item2', 'item3' ] ```

This too: ```python my_dict = { 'key1': 'value1', 'key2': 'value2' } ```

Python allows any indentation inside brackets.

Class Methods

Common mistake: ```python class MyClass: def my_method(self): # Error: no indent pass ```

**Fix:** ```python class MyClass: def my_method(self): pass ```

Everything inside class must be indented.

My Setup

I use: - 4 spaces always - Editor auto-converts tabs - Auto-format on save - Python extension in VS Code

Never had indentation errors after this setup.

Quick Checklist

- [ ] Use 4 spaces (not tabs) - [ ] Consistent indentation in each file - [ ] Put code after colons (:) - [ ] Use pass for empty blocks - [ ] Enable auto-format in editor

Bottom Line

Python's indentation is annoying at first. Then you realize it makes code cleaner.

Set up your editor properly once. Never worry about it again.