然后我们在finally块中关闭它。

    通过这种方式，我们确保数据库会话在请求后始终关闭。即使在处理请求时出现异常。

    但是您不能从退出代码中引发另一个异常（在yield之后）。可以查阅 [Dependencies with yield and HTTPException](https://fastapi.tiangolo.com/zh/tutorial/dependencies/dependencies-with-yield/#dependencies-with-yield-and-httpexception)

*然后，当在路径操作函数*中使用依赖项时，我们使用`Session`，直接从 SQLAlchemy 导入的类型声明它。

*这将为我们在路径操作函数*中提供更好的编辑器支持，因为编辑器将知道`db`参数的类型`Session`：

=== "Python 3.9+"

---

"_Мы использовали библиотеку **FastAPI** для создания сервера **REST**, к которому можно делать запросы для получения **прогнозов**. [для Ludwig]_"

<div style="text-align: right; margin-right: 10%;">Piero Molino, Yaroslav Dudin, and Sai Sumanth Miryala - <strong>Uber</strong> <a href="https://eng.uber.com/ludwig-v0-2/" target="_blank"><small>(ref)</small></a></div>

---

!!! check "😮 **FastAPI** "
    ⚙️ 📟 🔬 "🔗" 👈 🚚 💽 🆎 & 🔬, 🔁.

### <a href="https://webargs.readthedocs.io/en/latest/" class="external-link" target="_blank">Webarg</a>

➕1️⃣ 🦏 ⚒ ✔ 🔗 <abbr title="reading and converting to Python data">✍</abbr> 📊 ⚪️➡️ 📨 📨.

Webarg 🧰 👈 ⚒ 🚚 👈 🔛 🔝 📚 🛠️, 🔌 🏺.

⚫️ ⚙️ 🍭 🔘 💽 🔬. &amp; ⚫️ ✍ 🎏 👩‍💻.

⚫️ 👑 🧰 &amp; 👤 ✔️ ⚙️ ⚫️ 📚 💁‍♂️, ⏭ ✔️ **FastAPI**.

!!! info

    ```Python hl_lines="8"
    {!> ../../../docs_src/request_forms_and_files/tutorial001.py!}
    ```

The files and form fields will be uploaded as form data and you will receive the files and form fields.

And you can declare some of the files as `bytes` and some as `UploadFile`.

!!! warning

```Python hl_lines="8-15"
{!../../../docs_src/custom_request_and_route/tutorial001.py!}
```

### Create a custom `GzipRoute` class

Next, we create a custom subclass of `fastapi.routing.APIRoute` that will make use of the `GzipRequest`.

This time, it will overwrite the method `APIRoute.get_route_handler()`.

This method returns a function. And that function is what will receive a request and return a response.

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

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

```Python hl_lines="16-18"
{!../../../docs_src/custom_request_and_route/tutorial002.py!}
```

## 🛃 `APIRoute` 🎓 📻

👆 💪 ⚒ `route_class` 🔢 `APIRouter`:

```Python hl_lines="26"
{!../../../docs_src/custom_request_and_route/tutorial003.py!}
```

That way, you can create a token with an expiration of, let's say, 1 week. And then when the user comes back the next day with the token, you know that user is still logged in to your system.

case, it could be better to have only 2 servers and use a higher percentage of their resources (CPU, memory, disk, network bandwidth, etc).

On the other hand, if you have 2 servers and you are using **100% of their CPU and RAM**, at some point one process will ask for more memory, and the server will have to use the disk as "memory" (which can be thousands of times slower), or even **crash**. Or one process might need to do some computation and would have to wait until the CPU is free again....

Then, using the certificate, the client and the TLS Termination Proxy **decide how to encrypt** the rest of the **TCP communication**. This completes the **TLS Handshake** part.

After this, the client and the server have an **encrypted TCP connection**, this is what TLS provides. And then they can use that connection to start the actual **HTTP communication**.

There are some data structures that can contain other values, like `dict`, `list`, `set` and `tuple`. And the internal values can have their own type too.

These types that have internal types are called "**generic**" types. And it's possible to declare them, even with their internal types.

To declare those types and the internal types, you can use the standard Python module `typing`. It exists specifically to support these type hints.