Indentationerror: unindent does not match any outer indentation level, although the indentation looks correct

python

indentation

linting-tools

code-readability

byNikita Barsukov·Feb 23, 2025

An IndentationError typically indicates a mix of tabs and spaces in your Python code. Address this swiftly by adjusting your editor settings to convert tabs into spaces, ensuring consistent indentation throughout your code.

Track inconsistencies by using the tabnanny module:

#Launch the tabnanny! No candy for bad indents.
python -m tabnanny yourscript.py

Here's what a healthy indentation (4 spaces) looks like in Python:

#Caution: Indent with precision
def function():
    if condition: #Don't slide down the slippery slope of indentations
        do_action()

Remember folks, choose one and stick to it. While both are permissible, spaces are recommended over tabs.

Identifying the root cause

An IndentationError comes your way when Python faces ambiguity in defining code blocks due to inconsistent spacing. Now, what could bring this about? Let's examine the common culprits.

The common causes

Invisible Characters: They're the ninjas of the coding world. Spaces and Tabs may seem identical but could be causing all the havoc. An editor that reveals invisible characters like Sublime Text can help you spot the difference.
The Copy Pizazz: Code could get jumbled when being copied from one source to another. The fix? Paste as plain text and reformat.
Editor Settings: Your editor may be inserting tabs instead of spaces. Configure your editor to insert spaces; 4 spaces per tab is the convention.

To escape the cycle of errors, take these actions:

Royally Re-Indent: Employ your editor's indentation tools to replace those wayward spaces and tabs.
Configure Editor: Editors and IDEs usually include options for replacing tabs with spaces automatically and revealing invisible characters. Utilizing these settings can help avert indentation crises in the future.
Use Linting Tools: Tools like Flake8 can detect style and syntax errors before the code hits the runner's track, thus serving a preemptive strike against potential problems.

Effective indentation and readability

Beyond being an error fix, a well-indented code enhances readability and maintainability. It's like following traffic rules on the road to error-free coding.

Indentation management

Nested Blocks: Nested structures require careful handling. Misalignments are more likely to creep in loops or conditions.
Refactoring Matters: As codes get refactored and reorganized, extra vigilance is needed with indentation levels.
Hinge on Alignment: Align related lines to spot structural errors early and make the code easier to scan.

The performance angle

While indentation errors won't affect performance, align it with good coding practice. A well-indented code is often the sign of efficient code flow and well-formulated logic.

explain-codes / Python / Indentationerror: unindent does not match any outer indentation level, although the indentation looks correct

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