IndentationError: unexpected indent
IndentationError: expected an indented block
TabError: inconsistent use of tabs and spaces in indentation

Python uses indentation to define code blocks (instead of curly braces). If the indentation is wrong, Python can’t parse your code.

Fix 1: Unexpected Indent

# ❌ Extra indentation
def greet():
    print("hello")
        print("world")  # 💥 unexpected indent

# ✅ Consistent indentation
def greet():
    print("hello")
    print("world")

Fix 2: Expected an Indented Block

# ❌ Empty block
def greet():
# nothing here 💥

# ✅ Use pass for empty blocks
def greet():
    pass

# ❌ After if/for/while
if True:
print("hello")  # 💥 needs to be indented

# ✅
if True:
    print("hello")

Fix 3: Mixed Tabs and Spaces

The most annoying cause. Your file has both tabs and spaces, and they look the same.

# Show tabs vs spaces in your file
cat -A script.py
# Tabs show as ^I, spaces show as regular spaces

Fix in VS Code:

1. Open the file
2. Click “Spaces: 4” or “Tab Size: 4” in the bottom status bar
3. Select “Convert Indentation to Spaces”

Fix from command line:

# Replace tabs with 4 spaces
expand -t 4 script.py > script_fixed.py
mv script_fixed.py script.py

Prevent it: Add to VS Code settings:

{
  "editor.insertSpaces": true,
  "editor.tabSize": 4,
  "[python]": {
    "editor.insertSpaces": true,
    "editor.tabSize": 4
  }
}

Fix 4: Copy-Pasted Code

Code copied from websites or PDFs often has invisible characters or wrong indentation.

Fix: Select all the indentation on the pasted lines and re-type it manually.

The Rule

• Use 4 spaces per indentation level (Python standard)
• Never mix tabs and spaces
• Configure your editor to insert spaces when you press Tab