Python Data and State

Overview

Every data bug traces back to an unclear answer to three questions: who owns this data, where is it validated, and how far does it travel? This skill encodes boundary-first thinking — make ownership explicit, validate at the edge, and minimize what crosses a boundary.

Treat these defaults as starting points. When project constraints demand deviation, call out tradeoffs and compensating controls (tests, observability, rollback).

When to Use

• Data ownership is ambiguous or split across modules.
• Validation logic is scattered or duplicated instead of concentrated at ingress.
• Mutable state is shared across module or layer boundaries.
• Multiple modules participate in a single transaction.
• Configuration is stringly-typed, read lazily, or inconsistent across environments.
• Lifecycle of a data object (creation, transformation, persistence) spans unclear boundaries.