@app.get('/')
def results():
    results = some_library()
    return results
```

---

If your application (somehow) doesn't have to communicate with anything else and wait for it to respond, use `async def`.

---

If you just don't know, use normal `def`.

---

@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>Or use <code>async def</code>...</summary>

If your code uses `async` / `await`, use `async def`:

```Python hl_lines="9  14"
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")

<div class="termy">

```console
// Verwenden Sie das Kommando „serve“ nachdem Sie „build-all“ ausgeführt haben.
$ python ./scripts/docs.py serve

Warning: this is a very simple server. For development, use mkdocs serve instead.
This is here only to preview a site with translations already built.
Make sure you run the build-all command first.
Serving at: http://127.0.0.1:8008
```

</div>

<div class="termy">

```console
// Use the command "build-all", this will take a bit
$ python ./scripts/docs.py build-all

Building docs for: en
Building docs for: es
Successfully built docs for: es
```

</div>

这样会对每一种语言构建一个独立的文档站点，并最终把这些站点全部打包输出到 `./site/` 目录。



然后你可以使用命令 `serve` 来运行生成的站点：

<div class="termy">

```console
// Use the command "serve" after running "build-all"

    title: Tips on migrating from Flask to FastAPI and vice-versa
  - author: Ankit Anchlia
    author_link: https://linkedin.com/in/aanchlia21
    link: https://hackernoon.com/explore-how-to-effectively-use-jwt-with-fastapi
    title: Explore How to Effectively Use JWT With FastAPI
  - author: Nicoló Lino
    author_link: https://www.nlino.com
    link: https://github.com/softwarebloat/python-tracing-demo

<a href="https://fastapi.tiangolo.com/fastapi-people/#sponsors" class="external-link" target="_blank">Other sponsors</a>

## Враження

"_[...] I'm using **FastAPI** a ton these days. [...] I'm actually planning to use it for all of my team's **ML services at Microsoft**. Some of them are getting integrated into the core **Windows** product and some **Office** products._"

    example: Annotated[
        Optional[Any],
        typing_deprecated(
            "Deprecated in OpenAPI 3.1.0 that now uses JSON Schema 2020-12, "
            "although still supported. Use examples instead."
        ),
    ] = None


# Ref: https://json-schema.org/draft/2020-12/json-schema-core.html#name-json-schema-documents
# A JSON Schema MUST be an object or a boolean.

    ```

=== "Python 3.10+ non-Annotated"

    !!! tip
        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="7"
    {!> ../../../docs_src/dependencies/tutorial001_py310.py!}
    ```

=== "Python 3.8+ non-Annotated"

    !!! tip
        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="11"

    If you want something quick to copy and paste, don't use this example, use the last one below.

Then, when you create an instance of that `Settings` class (in this case, in the `settings` object), Pydantic will read the environment variables in a case-insensitive way, so, an upper-case variable `APP_NAME` will still be read for the attribute `app_name`.

        security_scopes.extend(dependency_scopes)
    if isinstance(dependency, SecurityBase):
        use_scopes: List[str] = []
        if isinstance(dependency, (OAuth2, OpenIdConnect)):
            use_scopes = security_scopes
        security_requirement = SecurityRequirement(
            security_scheme=dependency, scopes=use_scopes
        )
    sub_dependant = get_dependant(
        path=path,
        call=dependency,