fastapi

FastAPI Patterns

File Organization

Directory Structure

• routers/ - API route handlers
• schemas/ - Pydantic models for request/response validation
• repositories/ - Data access layer

project/
├── routers/
│   ├── users.py
│   └── items.py
├── schemas/
│   ├── user.py
│   └── item.py
└── repositories/
    ├── user_repository.py
    └── item_repository.py

Pydantic Models

Pydantic v2 Standards

• Use Pydantic v2 BaseModel with model_config
• Define schemas for all request/response models
• Use proper field types and validators

from pydantic import BaseModel, Field

class UserCreate(BaseModel):
    email: str = Field(..., description="User email address")
    name: str = Field(..., min_length=1, max_length=100)
    
    model_config = {
        "json_schema_extra": {
            "example": {
                "email": "[email protected]",
                "name": "John Doe"
            }
        }
    }

Route Handlers

Response Models

• All routes return response_model - Define explicit response types
• Use proper HTTP status codes
• Handle errors consistently

from fastapi import APIRouter, HTTPException, status
from typing import List

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

@router.post(
    "/",
    response_model=UserResponse,
    status_code=status.HTTP_201_CREATED
)
async def create_user(user_data: UserCreate) -> UserResponse:
    # Implementation

Background Tasks

Long-Running Operations

• Use background tasks for long jobs
• Use FastAPI's BackgroundTasks for non-critical operations
• Use task queues (Celery, etc.) for critical background work

from fastapi import BackgroundTasks

@router.post("/process")
async def process_data(
    data: ProcessingRequest,
    background_tasks: BackgroundTasks
):
    background_tasks.add_task(long_running_operation, data)
    return {"status": "processing", "message": "Task queued"}

Security

CSRF Protection

• Don't disable CSRF on JWT cookie endpoints - Maintain security
• Use proper authentication mechanisms
• Validate all inputs