Global Error Handling: Consistent API Error Responses with FastAPI

Why Error Handling Matters Without proper error handling, your API either crashes or returns confusing responses. Frontend developers need consistent, predictable error shapes to build against. The Standard Error Shape Every error in this API follows this exact structure: { "error": { "message": "Reason for the error", "status": 400 } } Consistent. Predictable. Professional. 3 Global Error Handlers 1. 404 Not Found @app.exception_handler(404) async def not_found_handler(request: Request, exc: HTTPException): return JSONResponse( status_code=404, content={ "error": { "message": "Resource not found", "status": 404, "path": str(request.url) } } ) 2. 400 Validation Error @app.exception_handler(RequestValidationError) async def validation_error_handler(request: Request, exc: RequestValidationError): return JSONResponse( status_code=400, content={ "error": { "message": "Invalid input data", "status": 400, "details": str(exc.errors()) } } ) 3. 500 Internal Server Error @app.exception_handler(