vertical-ordering

Vertical Ordering

Overview

Place caller functions above their callees. High-level logic first, implementation details below. Read top-down like a newspaper article.

This is the "Vertical Ordering" principle from Clean Code (Robert C. Martin, Chapter 5).

Core Pattern

# ✅ CORRECT: Caller above callee
def process_order(order):
    validate_order(order)
    submit_order(order)


def validate_order(order):
    ...


def submit_order(order):
    ...


# ❌ WRONG: Helpers defined before caller
def validate_order(order):
    ...


def submit_order(order):
    ...


def process_order(order):
    validate_order(order)
    submit_order(order)

Quick Reference

Scenario	Ordering
Extract a helper from a function	Helper goes below the function it was extracted from
Public API function calls private helpers	Public function first, private helpers below
Chain of calls: A → B → C	Order: A, then B, then C
Multiple callers share a helper	Helper goes below its first caller

Common Mistakes

• Defining before use — feels natural (like variable declaration) but hides the high-level flow. Readers see details before context.
• Alphabetical ordering — ignores call relationships. The reader has to jump around to follow the logic.
• Grouping all helpers at the top or bottom — loses the locality of related functions. Keep caller and callee close together.