## HTTPX

Auch wenn Ihre **FastAPI**-Anwendung normale `def`-Funktionen anstelle von `async def` verwendet, handelt es sich darunter immer noch um eine `async`hrone Anwendung.

## HTTPX

Even if your **FastAPI** application uses normal `def` functions instead of `async def`, it is still an `async` application underneath.

You can use `async def` or normal `def`.

And you can declare dependencies with `async def` inside of normal `def` *path operation functions*, or `def` dependencies inside of `async def` *path operation functions*, etc.

It doesn't matter. **FastAPI** will know what to do.

/// note

        this.err = new PrintWriter(toPsOrDef(err, System.err), true);
    }

    private PrintStream toPsOrDef(OutputStream outputStream, PrintStream def) {
        if (outputStream == null) {
            return def;
        }
        if (outputStream instanceof PrintStream ps) {
            return ps;
        }
        return new PrintStream(outputStream);
    }

    //

It is just a standard function that can receive parameters.

It can be an `async def` or normal `def` function, **FastAPI** will know how to handle it correctly.

In this case, the task function will write to a file (simulating sending an email).

And as the write operation doesn't use `async` and `await`, we define the function with normal `def`:

{* ../../docs_src/background_tasks/tutorial001.py hl[6:9] *}

## Add the background task

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>Or use <code>async def</code>...</summary>

If your code uses `async` / `await`, use `async def`:

```Python hl_lines="9  14"

    }

    private static String getMessage(Throwable error, String def) {
        if (error == null) {
            return def;
        }
        String msg = error.getMessage();
        if (msg != null && !msg.isEmpty()) {
            return msg;
        }
        return getMessage(error.getCause(), def);
    }

    private ArtifactRepositoryLayout getLayout(String id) {

It will be called by **FastAPI** whenever it receives a request to the URL "`/`" using a `GET` operation.

In this case, it is an `async` function.

---

You could also define it as a normal function instead of `async def`:

{* ../../docs_src/first_steps/tutorial003.py hl[7] *}

/// note

If you don't know the difference, check the [Async: *"In a hurry?"*](../async.md#in-a-hurry){.internal-link target=_blank}.

///

                            .add();
                }
                listPromptBuilder.addPrompt();
            } else if (field.getDefaultValue().isPresent()) {
                // input w/ def value
                promptBuilder
                        .createInputPrompt()
                        .name(fieldKey)
                        .message(fieldDescription)

```Python
def get_current_user(token: str):
    # authenticate user
    return User()


@app.get("/items/")
def read_items(user: User = Depends(get_current_user)):
    ...


@app.post("/items/")
def create_item(*, user: User = Depends(get_current_user), item: Item):
    ...


@app.get("/items/{item_id}")