from fastapi import FastAPI
from pydantic.v1 import BaseModel

app = FastAPI()


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

    class Config:
        schema_extra = {
            "examples": [
                {
                    "name": "Foo",
                    "description": "A very nice Item",
                    "price": 35.4,

Read more about them in the [FastAPI docs for Middleware](https://fastapi.tiangolo.com/advanced/middleware/).

::: fastapi.middleware.cors.CORSMiddleware

It can be imported from `fastapi`:

```python
from fastapi.middleware.cors import CORSMiddleware
```

::: fastapi.middleware.gzip.GZipMiddleware

It can be imported from `fastapi`:

```python
from fastapi.middleware.gzip import GZipMiddleware
```

* 可选的 `client_id`（本例未使用）
* 可选的 `client_secret`（本例未使用）

/// info | 说明

`OAuth2PasswordRequestForm` 与 `OAuth2PasswordBearer` 一样，都不是 FastAPI 的特殊类。

**FastAPI** 把 `OAuth2PasswordBearer` 识别为安全方案。因此，可以通过这种方式把它添加至 OpenAPI。

但 `OAuth2PasswordRequestForm` 只是可以自行编写的类依赖项，也可以直接声明 `Form` 参数。

但由于这种用例很常见，FastAPI 为了简便，就直接提供了对它的支持。

///

### 使用表单数据

/// tip | 提示

from fastapi import FastAPI
from pydantic import BaseModel, HttpUrl

app = FastAPI()


class Image(BaseModel):
    url: HttpUrl
    name: str


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


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

from dataclasses import dataclass, field

from fastapi import FastAPI


@dataclass
class Item:
    name: str
    price: float
    tags: list[str] = field(default_factory=list)
    description: str | None = None
    tax: float | None = None


app = FastAPI()


@app.get("/items/next", response_model=Item)
async def read_next_item():
    return {
        "name": "Island In The Moon",
        "price": 12.99,

from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None

    model_config = {
        "json_schema_extra": {
            "examples": [
                {
                    "name": "Foo",
                    "description": "A very nice Item",

    value_is_sequence,
)
from fastapi.background import BackgroundTasks
from fastapi.concurrency import (
    asynccontextmanager,
    contextmanager_in_threadpool,
)
from fastapi.dependencies.models import Dependant
from fastapi.exceptions import DependencyScopeError
from fastapi.logger import logger
from fastapi.security.oauth2 import SecurityScopes
from fastapi.types import DependencyCacheKey

你可以配置一些额外的 <a href="https://swagger.io/docs/open-source-tools/swagger-ui/usage/configuration/" class="external-link" target="_blank">Swagger UI 参数</a>.

如果需要配置它们，可以在创建 `FastAPI()` 应用对象时或调用 `get_swagger_ui_html()` 函数时传递 `swagger_ui_parameters` 参数。

`swagger_ui_parameters` 接受一个直接传递给 Swagger UI的字典，包含配置参数键值对。

FastAPI会将这些配置转换为 **JSON**，使其与 JavaScript 兼容，因为这是 Swagger UI 需要的。

## 不使用语法高亮

比如，你可以禁用 Swagger UI 中的语法高亮。

当没有改变设置时，语法高亮默认启用：

Successfully installed fastapi pydantic uvicorn
```

</div>

/// info

还有其他文件格式和工具来定义和安装依赖项。

 我将在下面的部分中向你展示一个使用 Poetry 的示例。 👇

///

### 创建 **FastAPI** 代码

* 创建`app`目录并进入。
* 创建一个空文件`__init__.py`。
* 创建一个 `main.py` 文件：



```Python
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def read_root():

  <a href="https://fastapi.tiangolo.com"><img src="https://fastapi.tiangolo.com/img/logo-margin/logo-teal.png" alt="FastAPI"></a>
</p>
<p align="center">
    FastAPI framework, high performance, easy to learn, fast to code, ready for production
</p>
<p align="center">
<a href="https://github.com/fastapi/fastapi/actions?query=workflow%3ATest+event%3Apush+branch%3Amaster" target="_blank">