What is python-standards?

A set of advanced standards for writing maintainable Python code in large projects. It covers interfaces, immutable data objects, error handling, dependency injection, and class design.

Use it whenever you implement Python code, especially domain models, services, data-transfer objects, interfaces, and business error handling.

It makes code easier to test, change, and maintain as the codebase and team grow, while reducing unnecessary coupling between parts of the system.

How systemowiec/ai-agents-workspace-starter configures Claude Code and

Reuse

Borrowing it

Nothing to install: this file belongs to systemowiec/ai-agents-workspace-starter. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/systemowiec/ai-agents-workspace-starter/main/.agents/skills/python-standards/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/systemowiec/ai-agents-workspace-starter

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/systemowiec/ai-agents-workspace-starter/python-standards/github.svg)](https://agentmods.dev/skills/systemowiec/ai-agents-workspace-starter/python-standards)

Your own site

<a href="https://agentmods.dev/skills/systemowiec/ai-agents-workspace-starter/python-standards"><img src="https://agentmods.dev/badge/skills/systemowiec/ai-agents-workspace-starter/python-standards/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/systemowiec/ai-agents-workspace-starter/python-standards"><img src="https://agentmods.dev/badge/skills/systemowiec/ai-agents-workspace-starter/python-standards.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 38 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,183 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00038	$0.02183
Opus 5.5	$0.00015	$0.00873
Sonnet 5.5	$0.00008	$0.00437
Haiku 4.5	$0.00004	$0.00218

Measured 2mo ago against content hash a51ee21376fb, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

python-standards 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 2mo 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.

.agents/skills/python-standards/SKILL.md · 125 lines

How it starts

The opening of the file, as written. The whole thing — 125 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill: Enterprise Python Standards

Principal/Staff-level Python patterns. NOT junior/mid rules. These standards produce code that scales, is testable, and is maintainable by large teams. Apply to ALL Python code in this project.

A. Architecture & Design

Protocols over ABC - Use typing.Protocol for interfaces, not abc.ABC. Protocols enable structural subtyping (duck typing with type safety) without inheritance coupling.
Frozen dataclasses for value objects - Immutable by default: @dataclass(frozen=True, slots=True). Mutable state only where explicitly needed.
Result pattern for expected failures - Return Result[T, E] (or T | ErrorType) instead of raising exceptions for business-level failures. Exceptions only for truly exceptional (unexpected) situations.
__slots__ on hot-path classes - Reduces memory footprint and attribute access time. Always on dataclasses (slots=True), domain models, and DTO/schema objects.
Composition over inheritance - Favor dependency injection and delegation. Inheritance allowed only for framework requirements (e.g., AgentExecutor).
Single Responsibility - One class = one reason to change. Max 500 lines/class, 50 lines/function. If a method needs a comment explaining "what it does", it should be a separate function.

B. Type System

Exhaustive type hints - Every function: params + return type. No Any unless interfacing with untyped libraries (and wrap it immediately).
TypeVar with bounds - T = TypeVar("T", bound=BaseModel) for generic functions operating on model subtypes.
ParamSpec for decorator preservation - Decorators must preserve wrapped function's signature: P = ParamSpec("P"), Callable[P, R].
TypeGuard for narrowing - Use TypeGuard[SpecificType] in filter/validation functions to enable type narrowing in callers.
Final for constants - All module-level constants annotated with Final. Prevents accidental reassignment.
Annotated for validation metadata - Annotated[int, Field(ge=0)] instead of runtime-only checks. Self-documenting constraints.
TYPE_CHECKING for circular imports - Import type-only dependencies inside if TYPE_CHECKING: block. Never restructure code just to avoid forward references.

Read the full file on GitHub · 125 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.

2mo ago First seen · 125 lines · 38 tokens per session scan A a51ee21376fb

Subscribe to this mod's changes

python-standards is a skill published in the GitHub repository systemowiec/ai-agents-workspace-starter (2 stars, last pushed 7mo ago), licensed MIT. It adds 38 tokens to every session and 2,183 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-08-31.

Languages Python

python-standards next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
python-standardssystemowiec/ai-agents-workspace-starter	Skill	2	7mo ago	MIT	A	38	Claude Code, Codex
matlabK-Dense-AI/scientific-agent-skills	Skill	56k	5d ago	MIT	A	44	Claude Code
pennylaneK-Dense-AI/scientific-agent-skills	Skill	56k	5d ago	MIT	A	74	Claude Code
holoscan-install-wheelNVIDIA/skills	Skill	3.9k	today	Apache-2.0	A	34	Claude Code, Codex
future-self-liteTHU-MAIC/OpenMAIC	Skill	43k	yesterday	MIT	A	20	Claude Code, Codex
rocm-kernelshuggingface/kernels	Skill	783	yesterday	Apache-2.0	A	93	Claude Code
typing-exclusion-workergetsentry/skills	Skill	1.1k	yesterday	Apache-2.0	A	57	Claude Code

ai-agents-workspace-starter: Skill for Claude Code