Rate limits and backoff

When the server asks you to slow down

429 Too Many Requests means you are going too fast. Politeness here is practical: an API that keeps rate-limiting you will eventually block you.

A 429 usually carries a Retry-After header saying how many seconds to wait. Honour it when it is there, and fall back to exponential backoff when it is not:

if r.status_code == 429:
    wait = float(r.headers.get("retry-after", 2 ** attempt))
    time.sleep(wait)
    continue

The fake /limited endpoint returns 429 once, with retry-after: 0, then succeeds.

Your turn: write fetch_polite(url, max_attempts=4) that honours Retry-After on a 429, returns the parsed body on success, and None if it never succeeds. Record the waits it performed in a module-level waits list rather than actually sleeping, so the behaviour can be checked.