#### `lru_cache` Technical Details

`@lru_cache` modifies the function it decorates to return the same value that was returned the first time, instead of computing it again, executing the code of the function every time.

app = FastAPI()


class InternalError(Exception):
    pass


def get_username():
    try:
        yield "Rick"
    except InternalError:
        print("Oops, we didn't raise again, Britney 😱")


@app.get("/items/{item_id}")
def get_item(item_id: str, username: Annotated[str, Depends(get_username)]):
    if item_id == "portal-gun":
        raise InternalError(

## Dependencies with `yield` and `except`

If you catch an exception using `except` in a dependency with `yield` and you don't raise it again (or raise a new exception), FastAPI won't be able to notice there was an exception, the same way that would happen with regular Python:

=== "Python 3.9+"

    ```Python hl_lines="15-16"

{!../../../docs_src/custom_docs_ui/tutorial002.py!}
```

### Include the custom docs for static files

And the same way as with a custom CDN, now you can create the *path operations* for the custom docs.

Again, you can re-use FastAPI's internal functions to create the HTML pages for the docs, and pass them the needed arguments:

    ```Python
    commons: CommonQueryParams = Depends()
    ```

You declare the dependency as the type of the parameter, and you use `Depends()` without any parameter, instead of having to write the full class *again* inside of `Depends(CommonQueryParams)`.

The same example would then look like:

=== "Python 3.10+"

    ```Python hl_lines="19"
    {!> ../../../docs_src/dependencies/tutorial004_an_py310.py!}
    ```

app = FastAPI()


class InternalError(Exception):
    pass


def get_username():
    try:
        yield "Rick"
    except InternalError:
        print("Oops, we didn't raise again, Britney 😱")


@app.get("/items/{item_id}")
def get_item(item_id: str, username: str = Depends(get_username)):
    if item_id == "portal-gun":
        raise InternalError(

And then they can try again knowing that it's probably something more similar to `stanleyjobsox` than to `johndoe`.

#### A "professional" attack

So, during that time, the computer can go and do some other work, while "slow-file" 📝 finishes.

Then the computer / program 🤖 will come back every time it has a chance because it's waiting again, or whenever it 🤖 finished all the work it had at that point. And it 🤖 will see if any of the tasks it was waiting for have already finished, doing whatever it had to do.

```Python hl_lines="18-20"
{!../../../docs_src/sql_databases_peewee/sql_app/main.py!}
```

For the **next request**, as we will reset that context variable again in the `async` dependency `reset_db_state()` and then create a new connection in the `get_db()` dependency, that new request will have its own database state (connection, transactions, etc).

!!! tip

🚥 1️⃣ 👆 🔗 📣 💗 🕰 🎏 *➡ 🛠️*, 🖼, 💗 🔗 ✔️ ⚠ 🎧-🔗, **FastAPI** 🔜 💭 🤙 👈 🎧-🔗 🕴 🕐 📍 📨.

&amp; ⚫️ 🔜 🖊 📨 💲 <abbr title="A utility/system to store computed/generated values, to re-use them instead of computing them again.">"💾"</abbr> &amp; 🚶‍♀️ ⚫️ 🌐 "⚓️" 👈 💪 ⚫️ 👈 🎯 📨, ↩️ 🤙 🔗 💗 🕰 🎏 📨.

🏧 😐 🌐❔ 👆 💭 👆 💪 🔗 🤙 🔠 🔁 (🎲 💗 🕰) 🎏 📨 ↩️ ⚙️ "💾" 💲, 👆 💪 ⚒ 🔢 `use_cache=False` 🕐❔ ⚙️ `Depends`:

```Python hl_lines="1"