La simplicidad del sistema de inyección de dependencias hace que **FastAPI** sea compatible con:

* todas las bases de datos relacionales
* bases de datos NoSQL
* paquetes externos
* APIs externas
* sistemas de autenticación y autorización
* sistemas de monitoreo de uso de la API
* sistemas de inyección de datos de response
* etc.

## Simple y Poderoso { #simple-and-powerful }

    "url": "https://docs.example.com/api-general",
}

app = FastAPI(openapi_external_docs=external_docs)


@app.api_route("/api_route")
def non_operation():
    return {"message": "Hello World"}


def non_decorated_route():
    return {"message": "Hello World"}


app.add_api_route("/non_decorated_route", non_decorated_route)


@app.get("/text")
def get_text():
    return "Hello World"

        .build()
    val call = client.newCall(request)

    // Check the Kotlin-focused APIs.
    assertThat(call.tag(String::class)).isEqualTo("hello")
    assertThat(call.tag(Integer::class)).isEqualTo(5)
    assertThat(call.tag(Boolean::class)).isNull()
    assertThat(call.tag(Any::class)).isNull()

    // Check the Java APIs too.
    assertThat(call.tag(String::class.java)).isEqualTo("hello")

    async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
        yield

    @asynccontextmanager
    async def router_lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
        yield

    router = APIRouter(lifespan=router_lifespan)
    app = FastAPI(lifespan=lifespan)
    app.include_router(router)

    with TestClient(app) as client:
        assert not client.app_state

///

* `app` 目錄包含所有內容。它有一個空的 `app/__init__.py` 檔案，所以它是一個「Python 套件」（「Python 模組」的集合）：`app`。
* 它包含一個 `app/main.py` 檔案。因為它在一個 Python 套件中（有 `__init__.py` 檔案的目錄），它是該套件的一個「模組」：`app.main`。
* 還有一個 `app/dependencies.py` 檔案，就像 `app/main.py` 一樣，它是一個「模組」：`app.dependencies`。
* 有一個子目錄 `app/routers/`，裡面有另一個 `__init__.py` 檔案，所以它是一個「Python 子套件」：`app.routers`。
* 檔案 `app/routers/items.py` 在一個套件 `app/routers/` 內，因此它是一個子模組：`app.routers.items`。

        warnings.simplefilter("always")
        monkeypatch.delattr("multipart.multipart.parse_options_header", raising=False)
    with pytest.raises(RuntimeError, match=multipart_incorrect_install_error):
        app = FastAPI()

        @app.post("/")
        async def root(username: str = Form()):
            return username  # pragma: nocover


def test_incorrect_multipart_installed_file_upload(monkeypatch):

from fastapi import FastAPI, Form
from fastapi.testclient import TestClient
from pydantic import BaseModel, Field

from .utils import get_body_model_name

app = FastAPI()

# =====================================================================================
# Without aliases


@app.post("/optional-str", operation_id="optional_str")
async def read_optional_str(p: Annotated[str | None, Form()] = None):
    return {"p": p}

from .utils import get_body_model_name

app = FastAPI()

# =====================================================================================
# Without aliases


@app.post("/optional-bytes", operation_id="optional_bytes")
async def read_optional_bytes(p: Annotated[bytes | None, File()] = None):
    return {"file_size": len(p) if p else None}


@app.post("/optional-uploadfile", operation_id="optional_uploadfile")

from .utils import get_body_model_name

app = FastAPI()

# =====================================================================================
# Without aliases


@app.post("/required-str", operation_id="required_str")
async def read_required_str(p: Annotated[str, Form()]):
    return {"p": p}


class FormModelRequiredStr(BaseModel):
    p: str

from .utils import get_body_model_name

app = FastAPI()

# =====================================================================================
# Without aliases


@app.post("/list-bytes", operation_id="list_bytes")
async def read_list_bytes(p: Annotated[list[bytes], File()]):
    return {"file_size": [len(file) for file in p]}


@app.post("/list-uploadfile", operation_id="list_uploadfile")