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IndentationError: What It Means and How to Fix It

Error reference

IndentationError

Language

Python

Severity

High

When it happens

An IndentationError is a specific form of SyntaxError raised in Python when the indentation of a block of code does not follow the expected pattern.

Potential fixes

Configure your editor to use spaces only (4 spaces per indent level is the Python convention). Enable 'show whitespace' in your editor to spot mixed tabs and spaces. Run your linter or formatter (such as ruff or black) to auto-fix indentation.

Related errors

SyntaxError

Deep dive

An IndentationError is a specific form of SyntaxError raised in Python when the indentation of a block of code does not follow the expected pattern. Python uses indentation to define code blocks, so inconsistent spaces or tabs cause this error.

Why it happens

  • •Mixing tabs and spaces for indentation in the same file.
  • •Using a different number of spaces for a line that should be at the same level.
  • •Accidentally removing or adding a space when editing code.
  • •Copying code from another source that uses a different indentation style.

Potential fixes

Configure your editor to use spaces only (4 spaces per indent level is the Python convention). Enable 'show whitespace' in your editor to spot mixed tabs and spaces. Run your linter or formatter (such as ruff or black) to auto-fix indentation.

Examples

Python

Code that triggers the error

def calculate(x):
    result = x * 2
  return result

Error output

  File "app.py", line 3
    return result
IndentationError: unindent does not match any outer indentation level

Fixed code

def calculate(x):
    result = x * 2
    return result

print(calculate(5))  # 10

Practice in English

How would you explain an IndentationError to a fellow dev? Choose the right phrase:

"I hit an error...

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