FastAPI: CORS の使い方

プログラム

main_cors.py

# ------------------------------------------------------------------
#	main_cors.py
#
#					Apr/12/2022
# ------------------------------------------------------------------
from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware

# ------------------------------------------------------------------
app = FastAPI()

origins = [
    "http://localhost",
    "http://localhost:8080",
]

app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)


# ------------------------------------------------------------------
@app.get("/")
def read_root():
    return {"Hello": "World"}


# ------------------------------------------------------------------
@app.get("/items/{item_id}")
def read_item(item_id: int, q: str = None):
    return {"item_id": item_id, "q": q}

# ------------------------------------------------------------------

サーバーの実行

uvicorn main_cors:app --reload

CORS の設定が出来ていないと次のようなエラーが出ます。

from origin 'https://example.com' has been blocked by CORS policy: 
No 'Access-Control-Allow-Origin' header is present 
on the requested resource.