Quick Answer

Fix inconsistent indentation (spaces vs tabs) that breaks Python's block structure.

Understanding the Issue

Python uses whitespace for block delimitation. The interpreter raises IndentationError when it encounters inconsistent spacing (commonly mixing tabs and spaces) or incorrect nesting levels. This differs from brace-delimited languages and requires proper editor configuration.

The Problem

This code demonstrates the issue:

Python Error 
def faulty():
print("Missing indent")  # Error
    print("Over-indented")  # May not match outer level

The Solution

Here's the corrected code:

Python Fixed 
# Solution: Standard 4-space indentation
def correct():
    print("Properly indented")
    if True:
        print("Nested block")

Key Takeaways

Configure your editor to show invisibles and enforce 4-space indentation.