### Small Errors Automatically Handled { #small-errors-automatically-handled }

When building web APIs with FastAPI, if there's an error in our code, FastAPI will normally contain it to the single request that triggered the error. 🛡

from typing import Annotated, Union

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: Annotated[Union[str, None], Query(title="Query string", min_length=3)] = None,
):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

# `UploadFile` class

You can define *path operation function* parameters to be of the type `UploadFile` to receive files from the request.

You can import it directly from `fastapi`:

```python
from fastapi import UploadFile
```

::: fastapi.UploadFile
    options:
        members:
            - file
            - filename
            - size
            - headers
            - content_type
            - read

from fastapi import Body, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item = Body(embed=True)):
    results = {"item_id": item_id, "item": item}

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item):
    results = {"item_id": item_id, "item": item}

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item):
    results = {"item_id": item_id, "item": item}

Damit können Sie das Modell an **mehreren Stellen wiederverwenden** und auch Validierungen und Metadaten für alle Parameter gleichzeitig deklarieren. 😎

/// note | Hinweis

Dies wird seit FastAPI Version `0.115.0` unterstützt. 🤓

///

/// tip | Tipp

Diese gleiche Technik gilt für `Query`, `Cookie` und `Header`. 😎

///

## Cookies mit einem Pydantic-Modell { #cookies-with-a-pydantic-model }

* `StaticFiles()` インスタンスを生成し、特定のパスに「マウント」。

{* ../../docs_src/static_files/tutorial001.py hl[2,6] *}

/// note | 技術詳細

`from starlette.staticfiles import StaticFiles` も使用できます。

**FastAPI**は、開発者の利便性のために、`starlette.staticfiles` と同じ `fastapi.staticfiles` を提供します。しかし、実際にはStarletteから直接渡されています。

///

### 「マウント」とは

「マウント」とは、特定のパスに完全な「独立した」アプリケーションを追加することを意味します。これにより、すべてのサブパスの処理がなされます。

import pytest
from fastapi import Depends, FastAPI, Security
from fastapi.security import OAuth2, OAuth2PasswordRequestFormStrict
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

reusable_oauth2 = OAuth2(
    flows={
        "password": {
            "tokenUrl": "token",
            "scopes": {"read:users": "Read the users", "write:users": "Create users"},
        }
    }
)

from typing import Optional

import pytest
from fastapi import Depends, FastAPI, Security
from fastapi.security import OAuth2, OAuth2PasswordRequestFormStrict
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

reusable_oauth2 = OAuth2(
    flows={
        "password": {
            "tokenUrl": "token",
            "scopes": {"read:users": "Read the users", "write:users": "Create users"},
        }