IndentationError 🐍 Python

IndentationError: unexpected indent / expected an indented block

Python’s block structure is broken — inconsistent indentation or mixed tabs and spaces.

Seen on: Python

Meaning

Indentation is syntax in Python. Every block after : must be indented consistently, and mixing tabs and spaces (TabError) is not allowed.

Common causes

  • Mixed tabs and spaces
  • Empty block after if/def/for (use pass)
  • Copy-pasted code with different indentation
  • Stray indentation on a top-level line

⚡ Quick fix

  1. Configure the editor to insert 4 spaces
  2. Convert tabs to spaces for the file
  3. Add pass to empty blocks

Detailed fix by platform

Python

  1. python -m tabnanny file.py reports ambiguous indentation.

How to diagnose

  1. Line — Reported line and block above
  2. Whitespace — Tabs vs spaces?

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