دورة الحياة والتنظيف مع yield

from contextlib import asynccontextmanager
from fastapi import FastAPI
from fastapi.testclient import TestClient
events = []
@asynccontextmanager
async def lifespan(app):
    events.append("startup")
    app.state.catalog = {"count": 2}
    try:
        yield
    finally:
        events.append("shutdown")
app = FastAPI(lifespan=lifespan)
@app.get("/catalog")
def catalog(): return app.state.catalog
with TestClient(app) as client:
    print(client.get("/catalog").json(), events.copy())
print(events)

{'count': 2} ['startup']
['startup', 'shutdown']

يسبق البدء الطلب ويلي الإغلاق السياق بملكية قاموس وقائمة فقط.

from typing import Annotated
from fastapi import Depends, FastAPI
from fastapi.responses import StreamingResponse
from fastapi.testclient import TestClient
async def resource():
    state = {"open": True}
    try:
        yield state
    finally:
        state["open"] = False
async def body(state):
    yield "open" if state["open"] else "closed"
app = FastAPI()
@app.get("/request-scope")
async def request_scope(state: Annotated[dict, Depends(resource)]):
    return StreamingResponse(body(state))
@app.get("/function-scope")
async def function_scope(state: Annotated[dict, Depends(resource, scope="function")]):
    return StreamingResponse(body(state))
with TestClient(app) as client:
    print(client.get("/request-scope").text)
    print(client.get("/function-scope").text)

open
closed

يحفظ الطلب المورد الاصطناعي أثناء التدفق وتغلقه الدالة قبله؛ والعرض للتوقيت لا تنفيذ مورد فعلي.