Query Params & Validation: Making APIs Flexible and Secure

What are Query Parameters? Query parameters let users filter and customize API responses without changing the endpoint itself. Instead of /products/electronics , you write: /products?category=electronics&limit=5 Clean, flexible, and powerful. What is Input Validation? Validation ensures bad data never enters your system. If a user sends an empty search term or a negative price, your API should reject it immediately, not crash later. My 3 Endpoints for Day 5 1. Search with Validation @app.get("/search") def search(q: str = Query(min_length=1, description="Search term")): return { "query": q, "message": f"Searching for: {q}" } If q is empty : FastAPI automatically returns a 422 error. No extra code needed. That's Pydantic doing the work. 2. Products with Optional Filters @app.get("/products") def get_products( category: str = Query(default="all"), limit: int = Query(default=10, ge=1, le=100) ): return { "category": category, "limit": limit, "message": f"Fetching {limit} products from: {c