# Background Tasks - `BackgroundTasks`

You can declare a parameter in a *path operation function* or dependency function with the type `BackgroundTasks`, and then you can use it to schedule the execution of background tasks after the response is sent.

You can import it directly from `fastapi`:

```python
from fastapi import BackgroundTasks
```

# Path Parameters

You can declare path "parameters" or "variables" with the same syntax used by Python format strings:

```Python hl_lines="6-7"
{!../../../docs_src/path_params/tutorial001.py!}
```

The value of the path parameter `item_id` will be passed to your function as the argument `item_id`.

**FastAPI** has a great community constantly growing.

There are many posts, articles, tools, and projects, related to **FastAPI**.

Here's an incomplete list of some of them.

!!! tip
    If you have an article, project, tool, or anything related to **FastAPI** that is not yet listed here, create a <a href="https://github.com/tiangolo/fastapi/edit/master/docs/en/data/external_links.yml" class="external-link" target="_blank">Pull Request adding it</a>.

First, we create a new database session with the new database.

We'll use an in-memory database that persists during the tests instead of the local file `sql_app.db`.

But the rest of the session code is more or less the same, we just copy it.

```Python hl_lines="8-13"
{!../../../docs_src/sql_databases/sql_app/tests/test_sql_app.py!}
```

!!! tip

    * With <a href="https://github.com/ciscorn/starlette-graphene3" class="external-link" target="_blank">starlette-graphene3</a>

## GraphQL with Strawberry

```

## 🔢 🔬: 🎈, 🌘 🌘 & 🌘 🌘

🔢 🔬 👷 `float` 💲.

📥 🌐❔ ⚫️ ▶️️ ⚠ 💪 📣 <abbr title="greater than"><code>gt</code></abbr> &amp; 🚫 <abbr title="greater than or equal"><code>ge</code></abbr>. ⏮️ ⚫️ 👆 💪 🚚, 🖼, 👈 💲 🔜 👑 🌘 `0`, 🚥 ⚫️ 🌘 🌘 `1`.

, `0.5` 🔜 ☑ 💲. ✋️ `0.0` ⚖️ `0` 🔜 🚫.

&amp; 🎏 <abbr title="less than"><code>lt</code></abbr>.

```Python hl_lines="11"

, 🗄 👍 🚫 ⚙️ 👁 `Bucket` 🎚 💗 "<abbr title="A sequence of code being executed by the program, while at the same time, or at intervals, there can be others being executed too.">🧵</abbr>Ⓜ",, 👥 💪 🤚 🥡 🔗 &amp; 🚶‍♀️ ⚫️ 👆 🚙 🔢:

```Python hl_lines="49-53"
{!../../../docs_src/nosql_databases/tutorial001.py!}
```

## 🌃

FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

# Security - First Steps

Let's imagine that you have your **backend** API in some domain.

And you have a **frontend** in another domain or in a different path of the same domain (or in a mobile application).

And you want to have a way for the frontend to authenticate with the backend, using a **username** and **password**.

We can use **OAuth2** to build that with **FastAPI**.

# General - How To - Recipes

Here are several pointers to other places in the docs, for general or frequent questions.

## Filter Data - Security

To ensure that you don't return more data than you should, read the docs for [Tutorial - Response Model - Return Type](../tutorial/response-model.md){.internal-link target=_blank}.

## Documentation Tags - OpenAPI