"karlskoga","karlskrona","karlstad","katrineholm","kil","kinda","kiruna","klippan","knivsta","kramfors","kristianstad","kristinehamn","krokoms","kumla","kungsbacka","kungsör","kungälv","kävlinge","köping","laholm","landskrona","laxå","lekeberg","leksand","lerum","lessebo","lidingö","lidköping","lilla edets","lindesbergs","linköpings","ljungby","ljusdals","ljusnarsbergs","lomma","ludvika","luleå","lunds","lycksele","lysekil","malmö","malung-sälen","malå","mariestad","marks","markaryd","mellerud",...

Es kann sich um eine `async def`- oder normale `def`-Funktion handeln. **FastAPI** weiß, wie damit zu verfahren ist.

In diesem Fall schreibt die Taskfunktion in eine Datei (den Versand einer E-Mail simulierend).

Und da der Schreibvorgang nicht `async` und `await` verwendet, definieren wir die Funktion mit normalem `def`:

```Python hl_lines="6-9"
{!../../docs_src/background_tasks/tutorial001.py!}
```