In Python, indentation is crucial because it defines the structure of the code. Unlike other programming languages that use symbols like braces {} to indicate code blocks, Python uses indentation. When you encounter the error “IndentationError: unindent does not match any outer indentation level,” it means that the code’s indentation is not aligned properly, causing Python to raise an error.

What is the “IndentationError: unindent does not match any outer indentation level”?

This error occurs when Python encounters a line of code that is indented incorrectly. In Python, every block of code (e.g., in functions, loops, or conditionals) must maintain a consistent level of indentation. If a line of code is indented in a way that doesn’t match the surrounding code block, Python will raise this error.

The error message “IndentationError: unindent does not match any outer indentation level” occurs in Python when the indentation of a line is not consistent with the rest of the code block. Python uses indentation to define the structure of code, such as loops, conditionals, and functions, so maintaining proper indentation is crucial for the program to run correctly.

Causes of the Error

1. Inconsistent Spaces and Tabs: Python treats spaces and tabs differently. If you mix them, the interpreter may get confused, leading to this error.
2. Misaligned Indentation: Code that is supposed to be part of a specific block (such as inside a loop or function) may not be properly aligned with the rest of the code at that level.
3. Improper Dedentation: When you end a block of code, the next line must be indented properly to match the outer scope, but if the unindentation doesn’t match the expected level, Python raises this error.

Example of the Error

def greet(name):
    if name:
        print(f"Hello, {name}")
      print("Welcome!")  # This line is incorrectly indented. IndentationError: unindent does not match any outer indentation level

In the above example, the line print("Welcome!") is not indented to the same level as the print(f"Hello, {name}") statement, even though both lines are part of the same block inside the if statement. This would cause an “IndentationError.”

Read Also: The Truth Value of a Series is Ambiguous. use a.empty, a.bool(), a.item(), a.any() or a.all().

Steps to Resolve the Issue

Here’s how you can resolve the “IndentationError: unindent does not match any outer indentation level” step by step:

1. Check for Consistent Indentation

Ensure that the indentation in your code is consistent. It’s common to use either 4 spaces per indentation level, or 1 tab, but you should not mix both. Stick to one type of indentation throughout the code.

For example:

def my_function():
    if True:
        print("Properly indented"). IndentationError: unindent does not match any outer indentation level

2. Set Your Editor to Use Spaces Instead of Tabs

Most editors allow you to configure whether tabs or spaces are used. Since spaces are recommended, ensure that your editor is set to replace tabs with spaces. In editors like VS Code or PyCharm:

• Look for settings that control indentation.
• Set it to convert tabs to spaces.
• Typically, set it to 4 spaces per indentation level.

3. Re-indent the Code Manually

If the error persists, you might have to manually reformat your code. Highlight the affected block and remove all indentation, then reapply the correct number of spaces (e.g., 4 spaces). This ensures that no hidden or mixed indentation characters are present.

For example:

# Incorrect indentation
def example():
     print("This will raise an error") # Extra space or tab

# Corrected indentation
def example():
    print("This will work")  # Proper 4-space indentation. IndentationError: unindent does not match any outer indentation level

4. Check for Hidden Indentation Characters

Sometimes, hidden characters like tabs may be present even if they are not visible. You can use the “Show Hidden Characters” feature in your editor to reveal any unexpected tabs or spaces that might be causing issues.

5. Use an IDE or Code Linter

Modern Integrated Development Environments (IDEs) like PyCharm or VS Code have built-in tools to detect and fix indentation problems. You can use their “Reformat Code” or “Fix Indentation” features to automatically correct the issue.

Alternatively, running a code linter like Flake8 can help identify problematic indentation and formatting issues, which you can fix accordingly.

Read Also: Botocore.Exceptions.Nocredentialserror: Unable to Locate Credentials: Mastering AWS Authentication

Conclusion

The “IndentationError: unindent does not match any outer indentation level” occurs when the indentation of a code block is inconsistent with the surrounding code. By following the steps outlined above, such as ensuring consistent use of spaces, configuring your editor, and re-indenting the code manually, you can quickly resolve the issue. Sticking to a standard indentation practice like using 4 spaces and leveraging modern IDEs can help prevent this error from happening again.