python

A set of practical guidelines for building and reviewing Python software. It covers code structure, input checking, web requests, asynchronous work, testing, and package setup.

In plain words
What is it for?
Use it when creating or reviewing Python services and libraries, adding web integrations or background tasks, configuring tests and packaging, or replacing hidden global state with explicit dependencies.
Why use it?
It helps prevent unclear types, invalid data, fragile network code, hidden dependencies, and inconsistent project conventions. It gives developers a shared standard for common Python decisions.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/kid-sid/codex-spellbook/python
Any agent
npx skills add kid-sid/codex-spellbook --skill python
Clone the repo
git clone --depth 1 https://github.com/kid-sid/codex-spellbook

Made for: Claude Code, Codex.

Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 678 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00043 $0.00678
Opus 5 $0.00022 $0.00339
Sonnet 5 $0.00009 $0.00136
Haiku 4.5 $0.00004 $0.00068

Measured 2d ago against content hash 16255e718f65, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

python scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

response = requests.get(url, timeout=30)
skills/python/SKILL.md · 101 lines

How it starts

The opening of the file, as written. The whole thing — 101 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Python

Prefer typed, explicit Python with validation at boundaries, modern async I/O, and simple seams over framework-heavy indirection.

When to Activate

  • Add or refactor Python modules
  • Choose a model type for request or domain data
  • Write an outbound HTTP integration
  • Add async handlers or background jobs
  • Configure pytest, typing, or packaging
  • Replace hidden globals with explicit dependencies
  • Review Python code for type and validation drift

Typing and Modeling

Pattern Preferred Avoid
Public functions Full parameter and return annotations Unannotated signatures
Collections list[str], dict[str, int] List, Dict unless compatibility requires it
Optional values `str None`
Need Use
External input validation pydantic.BaseModel
Internal immutable value object @dataclass(frozen=True)
Loosely structured mapping shape TypedDict

HTTP and Async

BAD

import requests

response = requests.get(url, timeout=30)

GOOD

import httpx

async with httpx.AsyncClient(timeout=10.0) as client:
    response = await client.get(url)
Rule Why
Use async only for real I/O boundaries Avoid fake async complexity
Do not call blocking I/O inside async handlers Prevent event loop stalls
Batch concurrent I/O with asyncio.TaskGroup or gather where safe Improve latency deterministically

Project Layout and DI

Section Purpose
[project] Metadata and dependencies
[tool.pytest.ini_options] Test discovery and markers
[tool.ruff] or [tool.black] Lint and format configuration
[tool.mypy] Type checking configuration
Preferred Avoid
Pass collaborators through constructors or function parameters Global singletons hidden inside modules
Build objects in a wiring layer Import-time side effects creating clients

Read the full file on GitHub · 101 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 101 lines · 43 tokens per session scan A 16255e718f65

Subscribe to this mod's changes

python is a skill published in the GitHub repository kid-sid/codex-spellbook (21 stars, last pushed 3mo ago), licensed MIT. It adds 43 tokens to every session and 678 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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