# Lifespan Events { #lifespan-events }

You can define logic (code) that should be executed before the application **starts up**. This means that this code will be executed **once**, **before** the application **starts receiving requests**.

The same way, you can define logic (code) that should be executed when the application is **shutting down**. In this case, this code will be executed **once**, **after** having handled possibly **many requests**.

@app.get("/items/{item_id}")
async def read_items(item_id: str):
    return items[item_id]


def test_read_items():
    # Before the lifespan starts, "items" is still empty
    assert items == {}

    with TestClient(app) as client:
        # Inside the "with TestClient" block, the lifespan starts and items added
        assert items == {"foo": {"name": "Fighters"}, "bar": {"name": "Tenders"}}

        response = client.get("/items/foo")

## `fastapi dev` { #fastapi-dev }

Das Ausführen von `fastapi dev` startet den Entwicklermodus.

`Depends()` erhält einen `scope`-Parameter, der sein kann:

* `"function"`: startet die Abhängigkeit vor der *Pfadoperation-Funktion*, die den Request bearbeitet, beendet die Abhängigkeit nach dem Ende der *Pfadoperation-Funktion*, aber **bevor** die Response an den Client zurückgesendet wird. Die Abhängigkeitsfunktion wird also **um** die *Pfadoperation-**Funktion*** **herum** ausgeführt.

## Details { #details }

The first `"/static"` refers to the sub-path this "sub-application" will be "mounted" on. So, any path that starts with `"/static"` will be handled by it.

The `directory="static"` refers to the name of the directory that contains your static files.

The `name="static"` gives it a name that can be used internally by **FastAPI**.

```console
$ pip install httpx
```

///

Import `TestClient`.

Create a `TestClient` by passing your **FastAPI** application to it.

Create functions with a name that starts with `test_` (this is standard `pytest` conventions).

Use the `TestClient` object the same way as you do with `httpx`.

### Neustart nach Absturz { #restart-after-crash }

Aber in den Fällen mit wirklich schwerwiegenden Fehlern, die den laufenden **Prozess** zum Absturz bringen, benötigen Sie eine externe Komponente, die den Prozess **neu startet**, zumindest ein paar Mal ...

/// tip | Tipp

        if (value != null) {
            return value;
        }
        return defaultValue;
    }

    /**
     * Determines if the given path represents a web crawling target.
     * Checks if the path starts with HTTP or HTTPS protocols.
     *
     * @param path the path to check
     * @return true if the path is a web crawling path, false otherwise
     */
    protected boolean isWebCrawlingPath(final String path) {

        return fileProtocols;
    }

    /**
     * Checks if the given URL uses a valid web protocol.
     *
     * @param url the URL to validate
     * @return true if the URL starts with a supported web protocol, false otherwise
     */
    public boolean isValidWebProtocol(final String url) {
        return stream(webProtocols).get(stream -> stream.anyMatch(s -> url.startsWith(s)));
    }

* `lang-all`: Translations
    * Use this for translations. You can normally quickly detect it by going to the "Files changed" tab in the PR and checking if the updated file(s) starts with `docs/{some lang}/docs` but not `docs/en/docs`. For example, `docs/es/docs`.