What does 'clean code' mean to you?

A "correct code" for me is code that meets the following criteria, prioritized:

1. Functionality and correctness: The code solves the assigned task, works without errors, and meets requirements.
2. Readability and clarity: The code is easy for other developers (and myself in the future) to understand. This is achieved through:
   • Meaningful names for variables, functions, and classes.
   • Consistent coding style (PEP 8 in Python).
   • Logical block separation.
   • Minimal use of "magic" numbers or constructs, unless justified.
3. Maintainability: The code is easy to modify, extend, and debug. This relates to readability but also includes:
   • Low coupling of components.
   • Modularity.
   • Test coverage.
4. Performance (if necessary): The code is resource-efficient (time and memory), especially when critical for the task. Premature optimization is discouraged.
5. Testability: The code is designed to be easily covered by automated tests.

An example of simple but "correct" code illustrating readability and clarity:

# Function to calculate the area of a rectangle
def calculate_rectangle_area(width, height):
    # Check for non-negative values, though omitted here for simplicity
    return width * height

# Using the function
rectangle_width = 10
rectangle_height = 5
area = calculate_rectangle_area(rectangle_width, rectangle_height)
# print(f"Rectangle area: {area}") # For output

A less "correct" (less readable) example:

def calc(w, h): # Unclear function and parameter names
    return w * h

In conclusion, "correct code" is a balance between functionality, clarity, and maintainability.