# Writing Python Services > Writing a class with encapsulated logic that interfaces with an external system. Logging, APIs, etc. Use when this capability is needed. - Skill: `tomevault-io/writing-python-services` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/writing-python-services` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/writing-python-services/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/writing-python-services --- - Use python 3.12+ syntax for types - e.g. `|` for unions, ` | None` for optional - No side effects in constructor - Use `@cached_property` and lazily evaluate properties needing IO - Methods use `dataclasses` for arguments and responses --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/jack-michaud) — claim your Tome and manage your conversions.