python.

Asyncio Taskgroup Vs Gather Error Handling

Uv Dependency Groups Pep 735 Vs Poetry

Pydantic v1 — historical, do NOT copy into v2 verbatim

fastapi-streaming-client-disconnect-cleanup

FastAPI async SQLAlchemy pool_pre_ping pool_recycle production

Tune `AsyncAdaptedQueuePool` with `pool_size=20`, `max_overflow=0`, `pool_pre_ping=True`, `pool_recycle=3600` under sustained FastAPI load — covers the mid-transaction disconnect that pre-ping cannot rescue and when to fall back to `NullPool` on serverless.

FastAPI Lifespan vs Startup/Shutdown: A Migration Guide That Won't Silently Break

Replace deprecated on_startup and on_shutdown handlers with FastAPI's lifespan async context manager. Covers stacking, exception propagation, and the silent-fail trap that catches most migrations.

FastAPI TestClient vs httpx.AsyncClient: When You Actually Need Async Tests

A practical comparison of FastAPI's sync TestClient and httpx.AsyncClient with ASGI transport, including fixture patterns and when each one is the right call.

Mocking AsyncAnthropic in pytest: autospec, Response Stubs, and Streaming

Mock the async Anthropic Python SDK in pytest with autospec=True, typed response stubs for messages.create, and async-iterator stubs for streaming completions.

FastAPI Request-ID Middleware: Correlation Across Upstream Services

Build a request-id + structured logging middleware in FastAPI using contextvars, a JSON formatter, and propagation rules that survive async hops and outbound httpx calls.

Pydantic Settings v2: Layered Env Config Without the Boilerplate

Build env-driven config in Python with Pydantic Settings v2 — nested models, layered .env overrides, validation, and secret types that survive logs.

FastAPI Background Tasks vs asyncio.create_task vs Redis Queue: When Each Fits

Compare FastAPI BackgroundTasks, asyncio.create_task, and Redis-backed queues like arq. Failure isolation, retry semantics, and the request-timeout boundary that decides which one you reach for.

uv Workspace Setup for a Multi-Package Python Monorepo

A working uv workspace layout for multi-package Python monorepos: root pyproject.toml, member pyproject.toml, local path dependencies, single lockfile strategy, and per-member commands.