python

A coding guide for Python backend services, meaning server-side programs that handle data, accounts, files, and outside services. It focuses on secure, maintainable, and performant code, including asynchronous work, testing, and type safety.

In plain words
What is it for?
Use it to build, review, test, and secure Python services for the JARVIS AI Assistant.
Why use it?
It helps reduce risks such as unsafe input handling, insecure saved data, command execution problems, and weak cryptography in backend 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/martinholovsky/claude-skills-generator/python
Any agent
npx skills add martinholovsky/claude-skills-generator --skill python
Clone the repo
git clone --depth 1 https://github.com/martinholovsky/claude-skills-generator

Made for: Claude Code, Codex.

Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,806 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 $0.00021 $0.03806
Opus 5 $0.00010 $0.01903
Sonnet 5 $0.00004 $0.00761
Haiku 4.5 $0.00002 $0.00381

Measured 2d ago against content hash 7911f285f607, 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.

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

result = subprocess.run(
skills/python/SKILL.md · 501 lines

How it starts

The opening of the file, as written. The whole thing — 501 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Python Backend Development Skill

File Organization

This skill uses a split structure for HIGH-RISK requirements:

  • SKILL.md: Core principles, patterns, and essential security (this file)
  • references/security-examples.md: Complete CVE details and OWASP implementations
  • references/advanced-patterns.md: Advanced Python patterns and optimization
  • references/threat-model.md: Attack scenarios and STRIDE analysis

Validation Gates

Gate Status Notes
0.1 Domain Expertise PASSED Type safety, async, security, testing
0.2 Vulnerability Research PASSED 5+ CVEs documented (2025-11-20)
0.5 Hallucination Check PASSED Examples tested on Python 3.11+
0.11 File Organization Split HIGH-RISK, ~450 lines + references

1. Overview

Risk Level: HIGH

Justification: Python backend services handle authentication, database access, file operations, and external API communication. Vulnerabilities in input validation, deserialization, command execution, and cryptography can lead to data breaches and system compromise.

You are an expert Python backend developer specializing in secure, maintainable, and performant services.

Core Expertise Areas

  • Type annotations and runtime validation
  • Async programming with asyncio
  • Security: input validation, cryptography, secrets management
  • Testing: pytest, property-based testing, security testing
  • Database access with SQLAlchemy/asyncpg
  • API development with FastAPI/Starlette

2. Core Responsibilities

Fundamental Principles

  1. TDD First: Write tests before implementation, design API through test cases
  2. Performance Aware: Use async, generators, efficient data structures by default
  3. Type Safety: Use type hints everywhere, validate at runtime boundaries
  4. Defense in Depth: Multiple validation layers, fail securely
  5. Secure Defaults: Use safe libraries, reject unsafe operations
  6. Explicit over Implicit: Clear error handling, explicit dependencies
  7. Testability: Design for testing, write security tests

Read the full file on GitHub · 501 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 501 lines · 21 tokens per session scan A 7911f285f607

Subscribe to this mod's changes

python is a skill published in the GitHub repository martinholovsky/claude-skills-generator (45 stars, last pushed 8mo ago), licensed Unlicense. It adds 21 tokens to every session and 3,806 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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