from fastapi import FastAPI
from fastapi.routing import APIRoute

app = FastAPI()


@app.get("/items/")
async def read_items():
    return [{"item_id": "Foo"}]


def use_route_names_as_operation_ids(app: FastAPI) -> None:
    """
    Simplify operation IDs so that generated API clients have simpler function
    names.

    Should be called only after all routes have been added.
    """
    for route in app.routes:

Dependencies are handled mainly with the special function `Depends()` that takes a callable.

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

For many scenarios, you can handle security (authorization, authentication, etc.) with dependencies, using `Depends()`.

from collections.abc import AsyncGenerator
from contextlib import asynccontextmanager

import pytest
from fastapi import APIRouter, FastAPI, Request
from fastapi.testclient import TestClient
from pydantic import BaseModel


class State(BaseModel):
    app_startup: bool = False
    app_shutdown: bool = False
    router_startup: bool = False
    router_shutdown: bool = False
    sub_router_startup: bool = False

## Utiliser la commande `fastapi run` { #use-the-fastapi-run-command }

En bref, utilisez `fastapi run` pour servir votre application FastAPI :

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> run <u style="text-decoration-style:solid">main.py</u>

  <span style="background-color:#009485"><font color="#D3D7CF"> FastAPI </font></span>  Starting production server 🚀

    Read more about it in the
    [FastAPI docs for HTTP Basic Auth](https://fastapi.tiangolo.com/advanced/security/http-basic-auth/).

    ## Example

    ```python
    from typing import Annotated

    from fastapi import Depends, FastAPI
    from fastapi.security import HTTPBasic, HTTPBasicCredentials

    app = FastAPI()

    security = HTTPBasic()

# Using Dataclasses { #using-dataclasses }

FastAPI is built on top of **Pydantic**, and I have been showing you how to use Pydantic models to declare requests and responses.

But FastAPI also supports using [`dataclasses`](https://docs.python.org/3/library/dataclasses.html) the same way:

{* ../../docs_src/dataclasses_/tutorial001_py310.py hl[1,6:11,18:19] *}

    * If you are comparing Starlette, compare it against Sanic, Flask, Django, etc. Web frameworks (or microframeworks).
* **FastAPI**:
    * The same way that Starlette uses Uvicorn and cannot be faster than it, **FastAPI** uses Starlette, so it cannot be faster than it.

# 從 Pydantic v1 遷移到 Pydantic v2 { #migrate-from-pydantic-v1-to-pydantic-v2 }

如果你有一個舊的 FastAPI 應用，可能正在使用 Pydantic 1 版。

FastAPI 0.100.0 同時支援 Pydantic v1 或 v2，會使用你已安裝的那個版本。

FastAPI 0.119.0 透過 Pydantic v2 內的 `pydantic.v1` 提供對 Pydantic v1 的部分支援，以便遷移到 v2。

FastAPI 0.126.0 移除了對 Pydantic v1 的支援，但在一段時間內仍支援 `pydantic.v1`。

/// warning

Pydantic 團隊自 **Python 3.14** 起，已停止在最新的 Python 版本中支援 Pydantic v1。

這也包含 `pydantic.v1`，在 Python 3.14 及以上版本不再支援。

# History, Design and Future { #history-design-and-future }

Some time ago, [a **FastAPI** user asked](https://github.com/fastapi/fastapi/issues/3#issuecomment-454956920):

> What’s the history of this project? It seems to have come from nowhere to awesome in a few weeks [...]

Here's a little bit of that history.

## Alternatives { #alternatives }

    in another `APIRouter` (ultimately included in the app).

    Read more about it in the
    [FastAPI docs for Bigger Applications - Multiple Files](https://fastapi.tiangolo.com/tutorial/bigger-applications/).

    ## Example

    ```python
    from fastapi import APIRouter, FastAPI

    app = FastAPI()
    router = APIRouter()