HTTP fundamentals: requests, status codes, JSON, httpx

HTTP has four verbs you'll use constantly: GET (read), POST (create), PUT (replace), DELETE (remove). Status codes come in families — 2xx succeeded, 3xx redirected, 4xx you made a bad request, 5xx the server broke. Knowing the family tells you where to look before you even read the message.

import httpx

r = httpx.get("https://api.example.com/users", params={"limit": 5})
r.raise_for_status()   # raises on 4xx/5xx instead of silently continuing
data = r.json()

httpx is the modern HTTP client for Python — the same API works for both sync (httpx.get) and async calls, which matters once you get to Lesson 7. raise_for_status() turns a bad response into an exception immediately, instead of your code continuing on with garbage data and failing somewhere confusing three lines later.

This is exactly the mechanism you'll use to call an LLM provider's API in Phase 2 — headers carry the API key, the body is JSON, and the response is JSON you parse and validate.