Errors and status codes in Python

HTTPException is how a handler refuses, with the status you choose.

from fastapi import FastAPI, HTTPException
from fastapi.responses import JSONResponse
from fastapi.testclient import TestClient

app = FastAPI()
TOURS = {"basics": 60}


class TourMissing(Exception):
    def __init__(self, slug):
        self.slug = slug


@app.exception_handler(TourMissing)
def handle_missing(request, exc):
    return JSONResponse(status_code=404, content={"error": exc.slug})


@app.get("/tours/{slug}")
def tour(slug: str):
    if slug == "gone":
        raise HTTPException(status_code=410, detail="that tour retired")
    if slug not in TOURS:
        raise TourMissing(slug)
    return {"slug": slug, "steps": TOURS[slug]}


client = TestClient(app)
print(client.get("/tours/basics").json())
print(client.get("/tours/gone").status_code, client.get("/tours/gone").json())
print(client.get("/tours/nope").status_code, client.get("/tours/nope").json())

How it works

1. Raise it; do not return an error dict with a 200.
2. detail is what the client sees in the body.
3. An exception handler maps your own error types onto responses.

Keywords and builtins used here

• TourMissing
• class
• def
• handle_missing
• if
• print
• raise
• return
• self
• str
• tour

The run, in numbers

Lines

31

Characters to type

830

Tokens

222

Three-star pace

110 tpm

At the three-star pace of 110 tokens a minute, this run takes about 121 seconds.

Type this snippet

Step 4 of 4 in FastAPI routes, step 9 of 19 in Web services & data access.

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