app = FastAPI()
router = APIRouter()


@router.get("/a", responses={501: {"description": "Error 1"}})
async def a():
    return "a"


@router.get(
    "/b",
    responses={
        502: {"description": "Error 2"},
        "4XX": {"description": "Error with range, upper"},
    },
)
async def b():
    return "b"


@router.get(
    "/c",
    responses={

## To `async` or not to `async` { #to-async-or-not-to-async }

As dependencies will also be called by **FastAPI** (the same as your *path operation functions*), the same rules apply while defining your functions.

You can use `async def` or normal `def`.

                } catch (InterruptedException e) {
                    log.debug("Async notification monitoring interrupted for {}", registrationId);
                    Thread.currentThread().interrupt();
                    break;
                } catch (Exception e) {
                    log.debug("Error in async notification monitoring for {}: {}", registrationId, e.getMessage());

import pytest
from httpx import ASGITransport, AsyncClient

from .main import app


@pytest.mark.anyio
async def test_root():
    async with AsyncClient(
        transport=ASGITransport(app=app), base_url="http://test"
    ) as ac:
        response = await ac.get("/")
    assert response.status_code == 200

## `async` oder nicht `async` { #to-async-or-not-to-async }

Da Abhängigkeiten auch von **FastAPI** aufgerufen werden (so wie Ihre *Pfadoperation-Funktionen*), gelten beim Definieren Ihrer Funktionen die gleichen Regeln.

Sie können `async def` oder einfach `def` verwenden.

    return user


async def get_current_user(token: str = Depends(oauth2_scheme)):
    user = fake_decode_token(token)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Not authenticated",
            headers={"WWW-Authenticate": "Bearer"},
        )
    return user

package schema

import (
	"reflect"
	"sync"
)

// sync pools
var (
	normalPool      sync.Map
	poolInitializer = func(reflectType reflect.Type) FieldNewValuePool {
		v, _ := normalPool.LoadOrStore(reflectType, &sync.Pool{
			New: func() interface{} {
				return reflect.New(reflectType).Interface()
			},
		})
		return v.(FieldNewValuePool)
	}

from typing import Annotated

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes, File(description="A file read as bytes")]):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(
    file: Annotated[UploadFile, File(description="A file read as UploadFile")],
):

from fastapi import FastAPI

app = FastAPI()


@app.get("/items/", tags=["items"])
async def read_items():
    return [{"name": "Foo", "price": 42}]


@app.get("/users/", tags=["users"])
async def read_users():
    return [{"username": "johndoe"}]


@app.get("/elements/", tags=["items"], deprecated=True)
async def read_elements():

class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None
    tags: list[str] = []


@app.post("/items/")
async def create_item(item: Item) -> Item:
    return item


@app.get("/items/")
async def read_items() -> list[Item]:
    return [
        Item(name="Portal Gun", price=42.0),
        Item(name="Plumbus", price=32.0),