* 交互式 API 文档将会自动更新，并加入新的请求体：

![Swagger UI](https://fastapi.tiangolo.com/img/index/index-03-swagger-02.png)

* 点击「Try it out」按钮，之后你可以填写参数并直接调用 API：

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

* 然后点击「Execute」按钮，用户界面将会和 API 进行通信，发送参数，获取结果并在屏幕上展示：

    ✋️ 👉 🖼 ☑ & ⚫️ 🎦 ❔ 🔗 ⏮️ 🔗 🦲.

👥 💪 ⚙️ 👉 🎏 🎯 🔐 📨 💪 ⚠ 🐕‍🦺.

🌐 👥 💪 🍵 📨 🔘 `try`/`except` 🍫:

```Python hl_lines="13  15"
{!../../../docs_src/custom_request_and_route/tutorial002.py!}
```

🚥 ⚠ 📉, `Request` 👐 🔜 ↔, 👥 💪 ✍ & ⚒ ⚙️ 📨 💪 🕐❔ 🚚 ❌:

```Python hl_lines="16-18"

    * `description`: a `str` with a short description for the external docs.
    * `url` (**required**): a `str` with the URL for the external documentation.

### Create metadata for tags

Let's try that in an example with tags for `users` and `items`.

Create metadata for your tags and pass it to the `openapi_tags` parameter:

```Python hl_lines="3-16  18"
{!../../../docs_src/metadata/tutorial004.py!}
```

But then you have to call "that method that converts the first letter to upper case".

Was it `upper`? Was it `uppercase`? `first_uppercase`? `capitalize`?

Then, you try with the old programmer's friend, editor autocompletion.

You type the first parameter of the function, `first_name`, then a dot (`.`) and then hit `Ctrl+Space` to trigger the completion.

But, sadly, you get nothing useful:

  "--strict-markers",
  "--ignore=docs_src",
]
xfail_strict = true
junit_family = "xunit2"
filterwarnings = [
    "error",
    # TODO: needed by asyncio in Python 3.9.7 https://bugs.python.org/issue45097, try to remove on 3.9.8
    'ignore:The loop argument is deprecated since Python 3\.8, and scheduled for removal in Python 3\.10:DeprecationWarning:asyncio',

You don't even have to check if the token exists to return an error. You can be sure that if your function is executed, it will have a `str` in that token.

You can try it already in the interactive docs:

<img src="/img/tutorial/security/image03.png">

We are not verifying the validity of the token yet, but that's a start already.

## Recap

Only one process can be handling the specific IP and port (the TLS Termination Proxy in our example) but the other applications/processes can be running on the server(s) too, as long as they don't try to use the same **combination of public IP and port**.

<img src="/img/deployment/https/https08.svg">

But you cannot convert from the gibberish back to the password.

### Why use password hashing

If your database is stolen, the thief won't have your users' plaintext passwords, only the hashes.

So, the thief won't be able to try to use that password in another system (as many users use the same password everywhere, this would be dangerous).

## Install `passlib`

PassLib is a great Python package to handle password hashes.

from typing import Annotated

from fastapi import Depends


async def dependency_a():
    dep_a = generate_dep_a()
    try:
        yield dep_a
    finally:
        dep_a.close()


async def dependency_b(dep_a: Annotated[DepA, Depends(dependency_a)]):
    dep_b = generate_dep_b()
    try:
        yield dep_b
    finally:
        dep_b.close(dep_a)

    ```

=== "🐍 3️⃣.9️⃣ & 🔛"

    ```Python hl_lines="13-18"
    {!> ../../../docs_src/sql_databases/sql_app_py39/main.py!}
    ```

!!! info
    👥 🚮 🏗 `SessionLocal()` & 🚚 📨 `try` 🍫.

     & ⤴️ 👥 🔐 ⚫️ `finally` 🍫.

    👉 🌌 👥 ⚒ 💭 💽 🎉 🕧 📪 ⏮️ 📨. 🚥 📤 ⚠ ⏪ 🏭 📨.