Engineering Craft › Clean Code & Principles

Consistency

Doing similar things the same way across a codebase.

Also known as: consistency, consistent style, coding style

Code style consistency means doing similar things the same way across a codebase: the same naming, structure, error handling and formatting everywhere. A codebase that looks like one person wrote it is far easier to read than one with five competing styles.

# Inconsistent: three ways to say the same thing
def getUser(id): ...
def fetch_order(order_id): ...
def LoadInvoice(inv): ...

# Consistent
def get_user(user_id): ...
def get_order(order_id): ...
def get_invoice(invoice_id): ...

Why it matters

• Less to think about. When everything follows a pattern, readers recognize it, and notice what’s different.
• Fewer pointless debates. Style arguments in reviews waste time.
• Easier changes. You can search and refactor mechanically when names and patterns are uniform.
• Smaller diffs, without whitespace noise.
• Fewer bugs, since odd code stands out.

What to be consistent about

• Formatting: indentation, line length, quotes.
• Naming: casing, verbs for functions, how to name booleans, abbreviations (naming).
• Structure: where files go, how modules are organized.
• Patterns: how errors are handled, how dependencies are passed, how tests are written.
• API conventions: URLs, response shapes, error formats.

How to get it

• Automate formatting with a formatter and checks with a linter, and enforce them in CI. Tools don’t argue.
• Write down the decisions that tools can’t check, in a short style guide or contributing doc.
• Follow the existing code when you add to it (following conventions).
• Review for it, kindly, and add automation when the same comment repeats.

Balance

Consistency within a codebase matters more than which style you pick. If you think the convention is wrong, propose changing it everywhere, with tooling to migrate, instead of introducing a second style. Don’t enforce consistency so rigidly that it blocks clear, better code in a new area. See clean code.