HTTP and status codes

from http import HTTPStatus
from fastapi import FastAPI, HTTPException, Header
from fastapi.testclient import TestClient
 
app = FastAPI()
DOCS = {"1": "Leave policy"}
 
@app.get("/docs/{doc_id}")
def get_doc(doc_id: str, authorization: str | None = Header(default=None)):
    if authorization != "Bearer demo-token":
        raise HTTPException(401, "missing or invalid token")          # who are you?
    if doc_id not in DOCS:
        raise HTTPException(404, "no such document")                  # it doesn't exist
    return {"id": doc_id, "title": DOCS[doc_id]}
 
@app.post("/ask", status_code=201)
def ask(body: dict):
    if len(body.get("question", "")) < 3:
        raise HTTPException(400, "question too short")                # your request is wrong
    if body["question"] == "quota":
        raise HTTPException(429, "rate limit exceeded", headers={"Retry-After": "30"})  # slow down
    return {"answer": "..."}
 
client = TestClient(app)
auth = {"Authorization": "Bearer demo-token"}
for method, path, kwargs in [
    ("GET", "/docs/1", {"headers": auth}),
    ("GET", "/docs/1", {}),
    ("GET", "/docs/9", {"headers": auth}),
    ("POST", "/ask", {"json": {"question": "What is RAG?"}}),
    ("POST", "/ask", {"json": {"question": "hi"}}),
    ("POST", "/ask", {"json": {"question": "quota"}}),
]:
    r = client.request(method, path, **kwargs)
    print(f"{method:4} {path:8} -> {r.status_code} {HTTPStatus(r.status_code).phrase:17} {r.json()}")

GET  /docs/1  -> 200 OK                {'id': '1', 'title': 'Leave policy'}
GET  /docs/1  -> 401 Unauthorized      {'detail': 'missing or invalid token'}
GET  /docs/9  -> 404 Not Found         {'detail': 'no such document'}
POST /ask     -> 201 Created           {'answer': '...'}
POST /ask     -> 400 Bad Request       {'detail': 'question too short'}
POST /ask     -> 429 Too Many Requests {'detail': 'rate limit exceeded'}