## Parâmetros opcionais

Da mesma forma, você pode declarar parâmetros de consulta opcionais, definindo o valor padrão para `None`:

//// tab | Python 3.10+

```Python hl_lines="7"
{!> ../../docs_src/query_params/tutorial002_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="9"
{!> ../../docs_src/query_params/tutorial002.py!}
```

////

```Python
from myapp import app
```

#### Mais detalhes

Digamos que seu arquivo se chama `myapp.py`.

Se você executá-lo com:

<div class="termy">

```console
$ python myapp.py
```

</div>

então a variável interna `__name__` no seu arquivo, criada automaticamente pelo Python, terá como valor a string `"__main__"`.

Então, a seção:

```Python

В предыдущем примере мы возвращали `словарь` из нашей зависимости:

//// tab | Python 3.10+

```Python hl_lines="9"
{!> ../../docs_src/dependencies/tutorial001_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="11"
{!> ../../docs_src/dependencies/tutorial001_an_py39.py!}
```

////

//// tab | Python 3.6+

```Python hl_lines="12"
{!> ../../docs_src/dependencies/tutorial001_an.py!}
```

Hello Wade Wilson
```

</div>

////

### 在 Python 中读取环境变量

您还可以在 Python 之外的地方（例如终端中或使用任何其他方法）创建环境变量，然后在 Python 中读取它们。

例如，您可以有一个名为 `main.py` 的文件，其中包含以下内容：

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip

Deklarieren wir also `tags` als Set von Strings.

//// tab | Python 3.10+

```Python hl_lines="12"
{!> ../../docs_src/body_nested_models/tutorial003_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="14"
{!> ../../docs_src/body_nested_models/tutorial003_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="1  14"
{!> ../../docs_src/body_nested_models/tutorial003.py!}

Ambas as *operações de rotas* requerem um cabeçalho `X-Token`.

//// tab | Python 3.10+

```Python
{!> ../../docs_src/app_testing/app_b_an_py310/main.py!}
```

////

//// tab | Python 3.9+

```Python
{!> ../../docs_src/app_testing/app_b_an_py39/main.py!}
```

////

//// tab | Python 3.8+

```Python
{!> ../../docs_src/app_testing/app_b_an/main.py!}
```

////

<div class="termy">

```console
$ python myapp.py
```

</div>

mais qui n'est pas appelé lorsqu'un autre fichier l'importe, comme dans :

```Python
from myapp import app
```

#### Pour davantage de détails

Imaginons que votre fichier s'appelle `myapp.py`.

Si vous l'exécutez avec :

<div class="termy">

```console
$ python myapp.py
```

</div>

//// tab | 🐍 3️⃣.6️⃣ & 🔛

```Python hl_lines="18  23"
{!> ../../docs_src/response_model/tutorial001_01.py!}
```

////

//// tab | 🐍 3️⃣.9️⃣ & 🔛

```Python hl_lines="18  23"
{!> ../../docs_src/response_model/tutorial001_01_py39.py!}
```

////

//// tab | 🐍 3️⃣.1️⃣0️⃣ & 🔛

```Python hl_lines="16  21"
{!> ../../docs_src/response_model/tutorial001_01_py310.py!}

# Setup Python
COPY setup.python.sh /setup.python.sh
COPY builder.requirements.txt /builder.requirements.txt
RUN /setup.python.sh python3.9 builder.requirements.txt
RUN /setup.python.sh python3.10 builder.requirements.txt
RUN /setup.python.sh python3.11 builder.requirements.txt
RUN /setup.python.sh python3.13 builder.requirements.txt

# Since we are using python3.12 as the default python version, we need to

//// tab | Python 3.9+

```Python hl_lines="6  14  22"
{!> ../../docs_src/dependencies/tutorial008_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="5  13  21"
{!> ../../docs_src/dependencies/tutorial008_an.py!}
```

////

//// tab | Python 3.8+ nicht annotiert

/// tip | "Tipp"