## Mounten einer **FastAPI**-Anwendung

„Mounten“ („Einhängen“) bedeutet das Hinzufügen einer völlig „unabhängigen“ Anwendung an einem bestimmten Pfad, die sich dann um die Handhabung aller unter diesem Pfad liegenden _Pfadoperationen_ kümmert, welche in dieser Unteranwendung deklariert sind.

### Hauptanwendung

from typing import Dict, List, Optional

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

app = FastAPI()


class Item(BaseModel):
    name: str = Field(alias="aliased_name")
    price: Optional[float] = None
    owner_ids: Optional[List[int]] = None


@app.get("/items/valid", response_model=Item)
def get_valid():
    return Item(aliased_name="valid", price=1.0)

from typing import Dict

from fastapi import FastAPI
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()


class Items(BaseModel):
    items: Dict[str, int]


@app.post("/foo")
def foo(items: Items):
    return items.items


client = TestClient(app)


def test_additional_properties_post():
    response = client.post("/foo", json={"items": {"foo": 1, "bar": 2}})

    <jsp:include page="/WEB-INF/view/common/admin/sidebar.jsp">
        <jsp:param name="menuCategoryType" value="system"/>
        <jsp:param name="menuType" value="dict"/>
    </jsp:include>
    <div class="content-wrapper">
        <div class="content-header">
            <div class="container-fluid">
                <div class="row mb-2">
                    <div class="col-sm-6">

from typing import Any, Callable, Dict, List, Optional, Sequence, Union

from fastapi import params
from fastapi._compat import Undefined
from fastapi.openapi.models import Example
from typing_extensions import Annotated, Doc, deprecated

_Unset: Any = Undefined


def Path(  # noqa: N802
    default: Annotated[
        Any,
        Doc(
            """
            Default value if the parameter field is not set.

from typing import Dict


def process_items(prices: Dict[str, float]):
    for item_name, item_price in prices.items():
        print(item_name)

## Em Detalhes

O marcador `@pytest.mark.anyio` informa ao pytest que esta função de teste deve ser invocada de maneira assíncrona:

```Python hl_lines="7"
{!../../docs_src/async_tests/test_main.py!}
```

/// tip | "Dica"

Note que a função de teste é `async def` agora, no lugar de apenas `def` como quando estávamos utilizando o `TestClient` anteriormente.

///

    <jsp:include page="/WEB-INF/view/common/admin/sidebar.jsp">
        <jsp:param name="menuCategoryType" value="system"/>
        <jsp:param name="menuType" value="dict"/>
    </jsp:include>
    <div class="content-wrapper">
        <div class="content-header">
            <div class="container-fluid">
                <div class="row mb-2">
                    <div class="col-sm-6">

    <jsp:include page="/WEB-INF/view/common/admin/sidebar.jsp">
        <jsp:param name="menuCategoryType" value="system"/>
        <jsp:param name="menuType" value="dict"/>
    </jsp:include>
    <div class="content-wrapper">
        <div class="content-header">
            <div class="container-fluid">
                <div class="row mb-2">
                    <div class="col-sm-6">

///

### Использование параметра `exclude_unset` в Pydantic

Если необходимо выполнить частичное обновление, то очень полезно использовать параметр `exclude_unset` в методе `.dict()` модели Pydantic.

Например, `item.dict(exclude_unset=True)`.