python-patterns

A guide for making Python design choices based on a project's needs, including web framework, asynchronous code, type checking, project structure, and error handling.

In plain words
What is it for?
Use it when starting or changing a Python application, especially when choosing between FastAPI, Django, and Flask or deciding whether asynchronous code is appropriate.
Why use it?
It helps avoid choosing tools by habit or copying examples that do not fit the project. It also makes trade-offs clear when requirements are uncertain.

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/phuonghx/aim-cli/python-patterns
Any agent
npx skills add phuonghx/aim-cli --skill python-patterns
Clone the repo
git clone --depth 1 https://github.com/phuonghx/aim-cli

Made for: Claude Code, Codex.

Per session 89 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,896 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 $0.00089 $0.01896
Opus 5 $0.00044 $0.00948
Sonnet 5 $0.00018 $0.00379
Haiku 4.5 $0.00009 $0.00190

Measured yesterday against content hash 4daaa37da0eb, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

python-patterns 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 yesterday.

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.

aim/templates/aim-agents/skills/python-patterns/SKILL.md · 211 lines

How it starts

The opening of the file, as written. The whole thing — 211 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Python Design Decisions

This is about reasoning, not memorization. Two projects rarely want the same answer, so avoid defaulting to one framework or one concurrency model. Where the requirements are ambiguous, name the trade-off and ask before deciding.

Choosing a web framework

Let the kind of application steer the choice:

  • API-first or microservices: FastAPI -- async-native, fast, modern.
  • Full-stack app, CMS, or heavy admin: Django -- everything is included.
  • Small tool, script, or teaching example: Flask -- minimal and flexible.
  • Serving ML/AI models: FastAPI -- Pydantic models, async, uvicorn.
  • Background processing: a queue like Celery alongside any of the above.

How they compare:

FastAPI Django Flask
Sweet spot APIs, services full-stack, CMS small, learning
Async native views/ORM (partial) via extensions
Admin UI build it built in via extensions
ORM bring your own Django ORM bring your own
Ramp-up gentle moderate gentle

Worth asking first: API-only or full-stack? Do you need an admin? Is the team comfortable with async? What infrastructure already exists?

Async or sync

Reach for async def when the work waits on the outside world and concurrency matters: database round-trips, HTTP calls, file I/O, lots of simultaneous connections, real-time features, service-to-service chatter -- and you are on an ASGI stack.

Stay with plain def when the work computes rather than waits, when the codebase or its libraries are blocking, when it is a simple script, or when the team is not yet fluent in async.

The rule of thumb:

Waiting on something external  ->  async
Burning CPU                    ->  sync, and parallelize with multiprocessing

Three things to avoid: blending sync and async without care, calling blocking libraries from async code, and forcing async onto CPU-bound work where it only adds overhead.

When you do go async, pick libraries that are actually async:

Read the full file on GitHub · 211 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. yesterday First seen · 211 lines · 89 tokens per session scan A 4daaa37da0eb

Subscribe to this mod's changes

python-patterns is a skill published in the GitHub repository phuonghx/aim-cli (1 stars, last pushed 2mo ago), licensed MIT. It adds 89 tokens to every session and 1,896 once invoked, about $0.0004 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 2026-08-31.

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