`0.5` wäre also ein gültiger Wert, aber nicht `0.0` oder `0`.

Das gleiche gilt für <abbr title="less than – kleiner als"><code>lt</code></abbr>.

# Response Status Code { #response-status-code }

The same way you can specify a response model, you can also declare the HTTP status code used for the response with the parameter `status_code` in any of the *path operations*:

* `@app.get()`
* `@app.post()`
* `@app.put()`
* `@app.delete()`
* etc.

{* ../../docs_src/response_status_code/tutorial001.py hl[6] *}

/// note

        override fun contentLength(): Long = 10

        override fun source(): BufferedSource = Buffer().writeUtf8("hello")
      }
    assertFailsWith<IOException> {
      body.bytes()
    }.also { expected ->
      assertThat(expected.message).isEqualTo(
        "Content-Length (10) and stream length (5) disagree",
      )
    }
  }

  @Test
  fun bytesThrowsMoreThanIntMaxValue() {

It has the same fields as `HeroBase`, and it also has `secret_name`.

Now, when the clients **create a new hero**, they will send the `secret_name`, it will be stored in the database, but those secret names won't be returned in the API to the clients.

/// tip

This is how you would handle **passwords**. Receive them, but don't return them in the API.

# Using Dataclasses { #using-dataclasses }

FastAPI is built on top of **Pydantic**, and I have been showing you how to use Pydantic models to declare requests and responses.

But FastAPI also supports using <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> the same way:

{* ../../docs_src/dataclasses/tutorial001.py hl[1,7:12,19:20] *}

Es wird also kein großer `str` zurückgegeben, der die Daten im JSON-Format (als String) enthält. Es wird eine Python-Standarddatenstruktur (z. B. ein `dict`) zurückgegeben, mit Werten und Unterwerten, die alle mit JSON kompatibel sind.

/// note | Hinweis

<img src="/img/python-types/image04.png">

Now you know that you have to fix it, convert `age` to a string with `str(age)`:

{* ../../docs_src/python_types/tutorial004.py hl[2] *}

## Declaring types { #declaring-types }

You just saw the main place to declare type hints. As function parameters.

This is also the main place you would use them with **FastAPI**.

# Environment Variables { #environment-variables }

/// tip

If you already know what "environment variables" are and how to use them, feel free to skip this.

///

An environment variable (also known as "**env var**") is a variable that lives **outside** of the Python code, in the **operating system**, and could be read by your Python code (or by other programs as well).

Wenn wir ein `dict` wie `user_dict` nehmen, und es einer Funktion (oder Klassenmethode) mittels `**user_dict` übergeben, wird Python es „entpacken“. Es wird die Schlüssel und Werte von `user_dict` direkt als Schlüsselwort-Argumente übergeben.

Wenn wir also das `user_dict` von oben nehmen und schreiben:

```Python
UserInDB(**user_dict)
```

dann ist das ungefähr äquivalent zu:

```Python
UserInDB(
    username="john",

    assertFailsWith<IllegalArgumentException> {
      windowUpdate(0)
    }.also { expected ->
      assertThat(expected.message)
        .isEqualTo("windowSizeIncrement == 0 || windowSizeIncrement > 0x7fffffffL: 0")
    }
    assertFailsWith<IllegalArgumentException> {
      windowUpdate(0x80000000L)
    }.also { expected ->
      assertThat(expected.message)