///

**FastAPI** 🔜 🏧 🛠️ ⚪️➡️ 📨, 👈 🔢 `item` 📨 ⚫️ 🎯 🎚 & 🎏 `user`.

⚫️ 🔜 🎭 🔬 ⚗ 💽, & 🔜 📄 ⚫️ 💖 👈 🗄 🔗 & 🏧 🩺.

## ⭐ 💲 💪

🎏 🌌 📤 `Query` & `Path` 🔬 ➕ 💽 🔢 & ➡ 🔢, **FastAPI** 🚚 🌓 `Body`.

🖼, ↔ ⏮️ 🏷, 👆 💪 💭 👈 👆 💚 ✔️ ➕1️⃣ 🔑 `importance` 🎏 💪, 🥈 `item` & `user`.

🚥 👆 📣 ⚫️, ↩️ ⚫️ ⭐ 💲, **FastAPI** 🔜 🤔 👈 ⚫️ 🔢 🔢.

    <img src="https://github.com/fastapi/fastapi/workflows/Test/badge.svg" alt="Test">
</a>
<a href="https://codecov.io/gh/fastapi/fastapi" target="_blank">
    <img src="https://img.shields.io/codecov/c/github/fastapi/fastapi?color=%2334D058" alt="Coverage">
</a>
<a href="https://pypi.org/project/fastapi" target="_blank">
    <img src="https://img.shields.io/pypi/v/fastapi?color=%2334D058&label=pypi%20package" alt="Package version">
</a>
</p>

---

from fastapi import FastAPI
from fastapi.responses import JSONResponse

app = FastAPI()


@app.post("/cookie/")
def create_cookie():
    content = {"message": "Come to the dark side, we have cookies"}
    response = JSONResponse(content=content)
    response.set_cookie(key="fakesession", value="fake-cookie-session-value")

    The dependency result will be a string containing the key value.

    ## Example

    ```python
    from fastapi import Depends, FastAPI
    from fastapi.security import APIKeyQuery

    app = FastAPI()

    query_scheme = APIKeyQuery(name="api_key")


    @app.get("/items/")
    async def read_items(api_key: str = Depends(query_scheme)):

import typing

from fastapi import FastAPI, Response
from fastapi.responses import JSONResponse
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()


class JsonApiResponse(JSONResponse):
    media_type = "application/vnd.api+json"


class Error(BaseModel):
    status: str
    title: str


class JsonApiError(BaseModel):
    errors: typing.List[Error]


@app.get(

from typing import List, Tuple

from fastapi import Depends, FastAPI, Security
from fastapi.security import SecurityScopes
from fastapi.testclient import TestClient

app = FastAPI()


def get_user(required_scopes: SecurityScopes):
    return "john", required_scopes.scopes


def get_user_override(required_scopes: SecurityScopes):
    return "alice", required_scopes.scopes


def get_data():
    return [1, 2, 3]

from fastapi import FastAPI, Response
from fastapi.responses import RedirectResponse

app = FastAPI()


@app.get("/portal", response_model=None)
async def get_portal(teleport: bool = False) -> Response | dict:
    if teleport:
        return RedirectResponse(url="https://www.youtube.com/watch?v=dQw4w9WgXcQ")

from typing import Optional

from fastapi import Depends, FastAPI, Security
from fastapi.security.open_id_connect_url import OpenIdConnect
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

oid = OpenIdConnect(openIdConnectUrl="/openid", auto_error=False)


class User(BaseModel):
    username: str


def get_current_user(oauth_header: Optional[str] = Security(oid)):
    if oauth_header is None:

...
```

#### OpenAPI 的用途

驱动 FastAPI 内置的 2 个交互式文档系统的正是 OpenAPI 模式。

并且还有数十种替代方案，它们全部都基于 OpenAPI。你可以轻松地将这些替代方案中的任何一种添加到使用 **FastAPI** 构建的应用程序中。

你还可以使用它自动生成与你的 API 进行通信的客户端代码。例如 web 前端，移动端或物联网嵌入程序。

## 分步概括

### 步骤 1：导入 `FastAPI`

```Python hl_lines="1"
{!../../docs_src/first_steps/tutorial001.py!}
```

`FastAPI` 是一个为你的 API 提供了所有功能的 Python 类。

/// note | "技术细节"

from datetime import datetime

from fastapi import FastAPI
from fastapi.encoders import jsonable_encoder
from pydantic import BaseModel

fake_db = {}


class Item(BaseModel):
    title: str
    timestamp: datetime
    description: str | None = None


app = FastAPI()


@app.put("/items/{id}")
def update_item(id: str, item: Item):
    json_compatible_item_data = jsonable_encoder(item)