python-development

A set of rules for working on Python projects. It covers Python versions, virtual-environment management, type hints, data structures, file paths, and dependency declarations for small scripts.

In plain words
What is it for?
Use it when developing Python software or standalone scripts. It guides environment setup with uv, type checking, function annotations, dataclasses, pathlib, and inline dependency metadata.
Why use it?
It keeps Python projects consistent and makes their dependencies and types easier to check. This reduces setup differences and helps catch errors before running the code.

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/sammcj/agentic-coding/python-development
Any agent
npx skills add sammcj/agentic-coding --skill python-development
Clone the repo
git clone --depth 1 https://github.com/sammcj/agentic-coding

Made for: Claude Code, Codex.

Per session 13 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 139 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. 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 $0.00013 $0.00139
Opus 5 $0.00006 $0.00069
Sonnet 5 $0.00003 $0.00028
Haiku 4.5 $0.00001 $0.00014

Measured 2d ago against content hash bcd3cad3839f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

python-development scanned grade A with 0 findings 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Skills/python-development/SKILL.md · 11 lines

What it actually says

Python

  • Favour Python 3.14+ features. Use uv for .venv management. Use uvx ty check for type checking
  • Type hints for all functions. Dataclasses for data structures. Pathlib over os.path. f-strings
  • For standalone scripts that have a few dependencies, use PEP 723 to declare dependencies in a TOML block inside # /// markers (e.g. # /// script\n# dependencies = [\n# "beautifulsoup4",\n# ]\n# ///)
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 · 11 lines · 13 tokens per session scan A bcd3cad3839f

Subscribe to this mod's changes

python-development is a skill published in the GitHub repository sammcj/agentic-coding (158 stars, last pushed 7d ago), licensed Apache-2.0. It adds 13 tokens to every session and 139 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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