fastapi-project-starter

Scaffold a production-ready async FastAPI application with SQLAlchemy 2.0, Alembic migrations, Pydantic v2, and structured logging.

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FastAPI Project Starter

Scaffold a production-ready async FastAPI application with SQLAlchemy 2.0, Alembic migrations, Pydantic v2, and structured logging.

Prerequisites

Python 3.12+
PostgreSQL 15+ (for asyncpg)
uv or pip for dependency management

Scaffold Command

mkdir -p src/app/{api/routes,core,db,models,schemas,services} tests
touch src/app/__init__.py src/app/api/__init__.py src/app/api/routes/__init__.py \
      src/app/core/__init__.py src/app/db/__init__.py src/app/models/__init__.py \
      src/app/schemas/__init__.py src/app/services/__init__.py tests/__init__.py

cat > pyproject.toml << 'PYPROJECT'
[project]
name = "app"
version = "0.1.0"
requires-python = ">=3.12"
dependencies = [
    "fastapi>=0.115.0",
    "uvicorn[standard]>=0.32.0",
    "pydantic>=2.9",
    "pydantic-settings>=2.6",
    "sqlalchemy[asyncio]>=2.0.36",
    "asyncpg>=0.30.0",
    "alembic>=1.14",
    "structlog>=24.4",
]

[project.optional-dependencies]
dev = [
    "pytest>=8.3",
    "pytest-asyncio>=0.24",
    "httpx>=0.27",
    "ruff>=0.8",
]

[tool.ruff]
target-version = "py312"
line-length = 99

[tool.ruff.lint]
select = ["E", "F", "I", "N", "UP", "B", "SIM", "ASYNC"]

[tool.pytest.ini_options]
asyncio_mode = "auto"
testpaths = ["tests"]
PYPROJECT

alembic init -t async src/app/db/migrations

# Initialize database
alembic upgrade head

Project Structure

project-root/
├── pyproject.toml
├── .env.example                    # Required env vars template
├── src/
│   └── app/
│       ├── __init__.py
│       ├── main.py              # Application entrypoint + lifespan
│       ├── api/
│       │   ├── __init__.py
│       │   ├── deps.py          # Shared dependencies (get_db, get_current_user)
│       │   └── routes/
│       │       ├── __init__.py
│       │       ├── health.py
│       │       └── users.py
│       ├── core/
│       │   ├── __init__.py
│       │   ├── config.py        # Pydantic Settings
│       │   └── logging.py       # structlog configuration
│       ├── db/
│       │   ├── __init__.py
│       │   ├── engine.py        # async engine + sessionmaker
│       │   ├── base.py          # DeclarativeBase
│       │   └── migrations/      # Alembic
│       │       ├── env.py
│       │       └── versions/
│       ├── models/
│       │   ├── __init__.py
│       │   └── user.py          # SQLAlchemy ORM models
│       ├── schemas/
│       │   ├── __init__.py
│       │   └── user.py          # Pydantic v2 schemas
│       └── services/
│           ├── __init__.py
│           └── user.py          # Business logic
└── tests/
    ├── __init__.py
    ├── conftest.py
    └── test_users.py

Key Conventions

All I/O is async. Use async def for route handlers, services, and DB access.
One router per resource file in api/routes/. Mount all routers via a parent APIRouter in api/routes/__init__.py.
Pydantic v2 schemas live in schemas/. ORM models live in models/. Never mix them.
Settings are loaded once via pydantic-settings and injected with Depends.
Database sessions are scoped per-request through a dependency.
Alembic env.py imports all models from models/__init__.py to detect changes.
Use structlog for all application logging. No print() statements.

Essential Patterns

Configuration (core/config.py)

from pydantic_settings import BaseSettings, SettingsConfigDict


class Settings(BaseSettings):
    model_config = SettingsConfigDict(env_file=".env", env_file_encoding="utf-8")

    app_name: str = "app"
    debug: bool = False
    database_url: str = "postgresql+asyncpg://postgres:postgres@localhost:5432/app"
    cors_origins: list[str] = ["http://localhost:3000"]


settings = Settings()

Database Engine (db/engine.py)

from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine

from app.core.config import settings

engine = create_async_engine(settings.database_url, echo=settings.debug)
async_session = async_sessionmaker(engine, expire_on_commit=False)

Declarative Base (db/base.py)

from sqlalchemy.orm import DeclarativeBase, MappedAsDataclass


class Base(DeclarativeBase, MappedAsDataclass):
    """Base class for all ORM models. Uses mapped_column dataclass style."""
    pass

ORM Model (models/user.py)

from datetime import datetime
from uuid import UUID, uuid4

from sqlalchemy import DateTime, func
from sqlalchemy.orm import Mapped, mapped_column

from app.db.base import Base


class User(Base):
    __tablename__ = "users"

    id: Mapped[UUID] = mapped_column(primary_key=True, default_factory=uuid4, init=False)
    email: Mapped[str] = mapped_column(unique=True, index=True)
    name: Mapped[str]
    is_active: Mapped[bool] = mapped_column(default=True)
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now(), init=False
    )

Pydantic Schemas (schemas/user.py)

from datetime import datetime
from uuid import UUID

from pydantic import BaseModel, EmailStr, ConfigDict


class UserCreate(BaseModel):
    email: EmailStr
    name: str


class UserRead(BaseModel):
    model_config = ConfigDict(from_attributes=True)

    id: UUID
    email: str
    name: str
    is_active: bool
    created_at: datetime

Dependencies (api/deps.py)

from collections.abc import AsyncGenerator

from sqlalchemy.ext.asyncio import AsyncSession

from app.db.engine import async_session


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    async with async_session() as session:
        yield session

Router (api/routes/users.py)

from uuid import UUID

from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.api.deps import get_db
from app.models.user import User
from app.schemas.user import UserCreate, UserRead

router = APIRouter(prefix="/users", tags=["users"])


@router.post("/", response_model=UserRead, status_code=status.HTTP_201_CREATED)
async def create_user(body: UserCreate, db: AsyncSession = Depends(get_db)) -> User:
    user = User(email=body.email, name=body.name)
    db.add(user)
    await db.commit()
    await db.refresh(user)
    return user


@router.get("/{user_id}", response_model=UserRead)
async def get_user(user_id: UUID, db: AsyncSession = Depends(get_db)) -> User:
    user = await db.get(User, user_id)
    if not user:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")
    return user

Router Aggregation (api/routes/init.py)

from fastapi import APIRouter

from app.api.routes.health import router as health_router
from app.api.routes.users import router as users_router

api_router = APIRouter(prefix="/api/v1")
api_router.include_router(health_router)
api_router.include_router(users_router)

Lifespan + App Factory (main.py)

from collections.abc import AsyncIterator
from contextlib import asynccontextmanager

import structlog
from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware

from app.api.routes import api_router
from app.core.config import settings
from app.core.logging import setup_logging


@asynccontextmanager
async def lifespan(app: FastAPI) -> AsyncIterator[None]:
    setup_logging()
    logger = structlog.get_logger()
    logger.info("application_startup", app_name=settings.app_name)
    yield
    logger.info("application_shutdown")


def create_app() -> FastAPI:
    app = FastAPI(title=settings.app_name, debug=settings.debug, lifespan=lifespan)

    app.add_middleware(
        CORSMiddleware,
        allow_origins=settings.cors_origins,
        allow_credentials=True,
        allow_methods=["*"],
        allow_headers=["*"],
    )

    app.include_router(api_router)
    return app


app = create_app()

Structured Logging (core/logging.py)

import logging

import structlog


def setup_logging(log_level: str = "INFO") -> None:
    structlog.configure(
        processors=[
            structlog.contextvars.merge_contextvars,
            structlog.stdlib.filter_by_level,
            structlog.stdlib.add_logger_name,
            structlog.stdlib.add_log_level,
            structlog.processors.TimeStamper(fmt="iso"),
            structlog.processors.StackInfoRenderer(),
            structlog.processors.format_exc_info,
            structlog.processors.JSONRenderer(),
        ],
        wrapper_class=structlog.stdlib.BoundLogger,
        context_class=dict,
        logger_factory=structlog.stdlib.LoggerFactory(),
        cache_logger_on_first_use=True,
    )
    logging.basicConfig(format="%(message)s", level=getattr(logging, log_level))

Background Task Example

from fastapi import BackgroundTasks

@router.post("/users/{user_id}/welcome")
async def send_welcome(user_id: UUID, background_tasks: BackgroundTasks):
    background_tasks.add_task(send_welcome_email, user_id)
    return {"status": "queued"}

Test (tests/conftest.py)

import pytest
from httpx import ASGITransport, AsyncClient

from app.main import create_app


@pytest.fixture
async def client():
    app = create_app()
    transport = ASGITransport(app=app)
    async with AsyncClient(transport=transport, base_url="http://test") as ac:
        yield ac

First Steps After Scaffold

Copy .env.example to .env and fill in values
Create virtual environment: python -m venv .venv && source .venv/bin/activate
Install dependencies: pip install -e ".[dev]" (or uv sync)
Run database migrations: alembic -c src/app/db/migrations/alembic.ini upgrade head
Start dev server: uvicorn app.main:app --reload --host 0.0.0.0 --port 8000 --app-dir src
Test the API: curl http://localhost:8000/docs

Common Commands

# Install dependencies
uv sync                      # or: pip install -e ".[dev]"

# Run development server
uvicorn app.main:app --reload --host 0.0.0.0 --port 8000 --app-dir src

# Create migration
alembic -c src/app/db/migrations/alembic.ini revision --autogenerate -m "add users table"

# Apply migrations
alembic -c src/app/db/migrations/alembic.ini upgrade head

# Run tests
pytest

# Lint and format
ruff check src tests
ruff format src tests

Integration Notes

Frontend (React/Next.js): FastAPI auto-generates OpenAPI spec at /docs. Use openapi-typescript-codegen or orval to generate a typed client from the schema.
Docker: Use a multi-stage Dockerfile. The uvicorn command serves as the production entrypoint; pair with gunicorn -k uvicorn.workers.UvicornWorker for multiple workers.
CI: Run ruff check, pytest, and alembic upgrade head (against a test DB) in pipeline.
Celery/ARQ: For heavy background work beyond BackgroundTasks, add arq with a shared Redis and define worker tasks in a workers/ package.

Repository: achreftlili/deep-dev-skills
Path: backend-python/fastapi-project-starter/SKILL.md
Commit: 181fcbc

Last updated: 4 hours ago
First committed: 7 months ago

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