fastapi-templates

name	fastapi-templates
description	Create production-ready FastAPI projects with async patterns, dependency injection, and comprehensive error handling. Use when building new FastAPI applications or setting up backend API projects. Use when this capability is needed.
metadata	{"author":"FeiWangHub"}

FastAPI Project Templates

Production-ready FastAPI project structures with async patterns, dependency injection, middleware, and best practices for building high-performance APIs.

When to Use This Skill

• Starting new FastAPI projects from scratch
• Implementing async REST APIs with Python
• Building high-performance web services and microservices
• Creating async applications with PostgreSQL, MongoDB
• Setting up API projects with proper structure and testing

Core Concepts

1. Project Structure

Recommended Layout:

app/
├── api/                    # API routes
│   ├── v1/
│   │   ├── endpoints/
│   │   │   ├── users.py
│   │   │   ├── auth.py
│   │   │   └── items.py
│   │   └── router.py
│   └── dependencies.py     # Shared dependencies
├── core/                   # Core configuration
│   ├── config.py
│   ├── security.py
│   └── database.py
├── models/                 # Database models
│   ├── user.py
│   └── item.py
├── schemas/                # Pydantic schemas
│   ├── user.py
│   └── item.py
├── services/               # Business logic
│   ├── user_service.py
│   └── auth_service.py
├── repositories/           # Data access
│   ├── user_repository.py
│   └── item_repository.py
└── main.py                 # Application entry

2. Dependency Injection

FastAPI's built-in DI system using Depends:

• Database session management
• Authentication/authorization
• Shared business logic
• Configuration injection

3. Async Patterns

Proper async/await usage:

• Async route handlers
• Async database operations
• Async background tasks
• Async middleware

Implementation Patterns

Pattern 1: Complete FastAPI Application

# main.py
from fastapi import FastAPI, Depends
from fastapi.middleware.cors import CORSMiddleware
from contextlib import asynccontextmanager
@asynccontextmanager
async def lifespan(app: FastAPI):
    """Application lifespan events."""
    # Startup
    await database.connect()
    yield
    # Shutdown
    await database.disconnect()
app = FastAPI(
    title="API Template",
    version="1.0.0",
    lifespan=lifespan
)
# CORS middleware
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)
# Include routers
from app.api.v1.router import api_router
app.include_router(api_router, prefix="/api/v1")
# core/config.py
from pydantic_settings import BaseSettings
from functools import lru_cache
class Settings(BaseSettings):
    """Application settings."""
    DATABASE_URL: str
    SECRET_KEY: str
    ACCESS_TOKEN_EXPIRE_MINUTES: int = 30
    API_V1_STR: str = "/api/v1"
    class :
        env_file = 

 () -> Settings:
     Settings()

 sqlalchemy.ext.asyncio  create_async_engine, AsyncSession
 sqlalchemy.ext.declarative  declarative_base
 sqlalchemy.orm  sessionmaker
 app.core.config  get_settings
settings = get_settings()
engine = create_async_engine(
    settings.DATABASE_URL,
    echo=,
    future=
)
AsyncSessionLocal = sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=
)
Base = declarative_base()
  () -> AsyncSession:
    
      AsyncSessionLocal()  session:
        :
             session
             session.commit()
         Exception:
             session.rollback()
            
        :
             session.close()

Pattern 2: CRUD Repository Pattern

# repositories/base_repository.py
from typing import Generic, TypeVar, Type, Optional, List
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select
from pydantic import BaseModel
ModelType = TypeVar("ModelType")
CreateSchemaType = TypeVar("CreateSchemaType", bound=BaseModel)
UpdateSchemaType = TypeVar("UpdateSchemaType", bound=BaseModel)
class BaseRepository(Generic[ModelType, CreateSchemaType, UpdateSchemaType]):
    """Base repository for CRUD operations."""
    def __init__(self, model: Type[ModelType]):
        self.model = model
    async def get(self, db: AsyncSession, id: int) -> Optional[ModelType]:
        """Get by ID."""
        result = await db.execute(
            select(self.model).where(self.model.id == id)
        )
        return result.scalars().first()
    async def get_multi(
        self,
        db: AsyncSession,
        skip: int = 0,
        limit: int = 100
    ) -> [ModelType]:
        
        result =  db.execute(
            select(.model).offset(skip).limit(limit)
        )
         result.scalars().()
      () -> ModelType:
        
        db_obj = .model(**obj_in.())
        db.add(db_obj)
         db.flush()
         db.refresh(db_obj)
         db_obj
      () -> ModelType:
        
        update_data = obj_in.(exclude_unset=)
         field, value  update_data.items():
            (db_obj, field, value)
         db.flush()
         db.refresh(db_obj)
         db_obj
      () -> :
        
        obj =  .get(db, )
         obj:
             db.delete(obj)
             
         

Pattern 3: Service Layer

# services/user_service.py
from typing import Optional
from sqlalchemy.ext.asyncio import AsyncSession
from app.repositories.user_repository import user_repository
from app.schemas.user import UserCreate, UserUpdate, User
from app.core.security import get_password_hash, verify_password
class UserService:
    """Business logic for users."""
    def __init__(self):
        self.repository = user_repository
    async def create_user(
        self,
        db: AsyncSession,
        user_in: UserCreate
    ) -> User:
        """Create new user with hashed password."""
        # Check if email exists
        existing = await self.repository.get_by_email(db, user_in.email)
        if existing:
            raise ValueError("Email already registered")
        # Hash password
        user_in_dict = user_in.dict()
        user_in_dict["hashed_password"] = get_password_hash(user_in_dict.pop("password"))
        # Create user
        user = await self.repository.create(db, UserCreate(**user_in_dict))
        return user

Pattern 4: API Endpoints with Dependencies

# api/v1/endpoints/users.py
from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy.ext.asyncio import AsyncSession
from typing import List
from app.core.database import get_db
from app.schemas.user import User, UserCreate, UserUpdate
from app.services.user_service import user_service
from app.api.dependencies import get_current_user
router = APIRouter()
@router.post("/", response_model=User, status_code=status.HTTP_201_CREATED)
async def create_user(
    user_in: UserCreate,
    db: AsyncSession = Depends(get_db)
):
    """Create new user."""
    try:
        user = await user_service.create_user(db, user_in)
        return user
    except ValueError as e:
        raise HTTPException(status_code=400, detail=str(e))

Testing

# tests/test_users.py
import pytest
@pytest.mark.asyncio
async def test_create_user(client):
    response = await client.post(
        "/api/v1/users/",
        json={
            "email": "[e-mail]",
            "password": "testpass123",
            "name": "Test User"
        }
    )
    assert response.status_code == 201
    data = response.json()
    assert data["email"] == "[e-mail]"
    assert "id" in data

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