`PUT` wird verwendet, um Daten zu empfangen, die die existierenden Daten ersetzen sollen.

### Warnung bezüglich des Ersetzens { #warning-about-replacing }

Das bedeutet, dass, wenn Sie den Artikel `bar` aktualisieren wollen, mittels `PUT` und folgendem Body:

```Python
{
    "name": "Barz",
    "price": 3,
    "description": None,
}
```

    [
        "/optional-list-bytes",
        "/optional-list-uploadfile",
    ],
)
def test_optional_list(path: str):
    client = TestClient(app)
    response = client.post(path, files=[("p", b"hello"), ("p", b"world")])
    assert response.status_code == 200
    assert response.json() == {"file_size": [5, 5]}


# =====================================================================================
# Alias

                status_code = str(route.status_code)
            else:
                # It would probably make more sense for all response classes to have an
                # explicit default status_code, and to extract it from them, instead of
                # doing this inspection tricks, that would probably be in the future
                # TODO: probably make status_code a default class attribute for all

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip | Consejo

El segundo argumento de <a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> es el valor por defecto a retornar.

Si no se proporciona, es `None` por defecto; aquí proporcionamos `"World"` como el valor por defecto para usar.

///

from fastapi import FastAPI

app = FastAPI()


@app.get("/app")
def read_main():
    return {"message": "Hello World from main app"}


subapi = FastAPI()


@subapi.get("/sub")
def read_sub():
    return {"message": "Hello World from sub API"}

    private final CoreExtension extension;

    public ExtensionResolutionException(CoreExtension extension, Throwable cause) {
        super(
                "Extension " + extension.getId() + " or one of its dependencies could not be resolved: "
                        + cause.getMessage(),
                cause);
        this.extension = extension;
    }

    /**
     * Constructor accepting the new API type for internal use.
     *

                return f"Hello {q}"
            else:
                return "Hello World"

    client = TestClient(app)
    return client


@needs_py310
def test_query_params_str_validations_no_query():
    client = get_client()
    response = client.get("/items/")
    assert response.status_code == 200
    assert response.json() == "Hello World"


@needs_py310
def test_query_params_str_validations_q_fixedquery():

from fastapi import FastAPI
from fastapi.responses import JSONResponse

app = FastAPI()


@app.get("/headers/")
def get_headers():
    content = {"message": "Hello World"}
    headers = {"X-Cat-Dog": "alone in the world", "Content-Language": "en-US"}

### Use cases: external service { #use-cases-external-service }

An example could be that you have an external authentication provider that you need to call.

You send it a token and it returns an authenticated user.

            return False

    return True


def _should_embed_body_fields(fields: list[ModelField]) -> bool:
    if not fields:
        return False
    # More than one dependency could have the same field, it would show up as multiple
    # fields but it's the same one, so count them by name
    body_param_names_set = {field.name for field in fields}
    # A top level field has to be a single field, not multiple