### The main app file

Now we create a dependency that returns a new `config.Settings()`.

//// tab | Python 3.9+

```Python hl_lines="6  12-13"
{!> ../../docs_src/settings/app02_an_py39/main.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="6  12-13"
{!> ../../docs_src/settings/app02_an/main.py!}
```

////

						<exclude>META-INF/**</exclude>
						<exclude>src/main/java/jcifs/dcerpc/msrpc/netdfs.java</exclude>
						<exclude>src/main/java/jcifs/dcerpc/msrpc/srvsvc.java</exclude>
						<exclude>src/main/java/jcifs/dcerpc/msrpc/samr.java</exclude>
						<exclude>src/main/java/jcifs/dcerpc/msrpc/lsarpc.java</exclude>
						<exclude>src/main/java/jcifs/dcerpc/rpc.java</exclude>
						<exclude>src/main/java/jcifs/smb1/**</exclude>
					</excludes>

    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

// It has extra helper functions for handling any/struct/marshal protobuf pain
type Wrapper struct {
	*admin.Clusters
}

// MarshalJSON is a custom marshaller to handle protobuf pain
func (w *Wrapper) MarshalJSON() ([]byte, error) {
	return protomarshal.Marshal(w)
}

// UnmarshalJSON is a custom unmarshaller to handle protobuf pain
func (w *Wrapper) UnmarshalJSON(b []byte) error {
	cd := &admin.Clusters{}

```console
// Hier stellen we de omgevingsvariabelen nog niet in
$ python main.py

// Omdat we de omgevingsvariabelen niet hebben ingesteld, krijgen we de standaardwaarde

Hello World from Python

// Maar als we eerst een omgevingsvariabele aanmaken
$ export MY_NAME="Wade Wilson"

// en het programma dan opnieuw aanroepen
$ python main.py

// kan het de omgevingsvariabele nu wel uitlezen

<div class="termy">

```console
// Here we don't set the env var yet
$ python main.py

// As we didn't set the env var, we get the default value

Hello World from Python

// But if we create an environment variable first
$ export MY_NAME="Wade Wilson"

// And then call the program again
$ python main.py

// Now it can read the environment variable

Hello Wade Wilson from Python
```

它也被設計成可作為未來的參考，讓你隨時回來查看所需的內容。

## 運行程式碼

所有程式碼區塊都可以直接複製和使用（它們實際上是經過測試的 Python 檔案）。

要運行任何範例，請將程式碼複製到 `main.py` 檔案，並使用以下命令啟動 `fastapi dev`：

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:single">main.py</u>
<font color="#3465A4">INFO    </font> Using path <font color="#3465A4">main.py</font>

    # o generateOutputDirectory: (NotRequired - Default Java:'../src/main/java' CSharp:'../source')
    #  The base output directory for generating.
    #  Basically you don't need to specify this if the project style is as follows:
    #
    #   *Java Project Style
    #     If this value is '../src/main/java' and your project is under the Maven,
    #     you don't need to set up this property!
    #

    #  Elements of this map are as below:
    #   o url: (NotRequired - Default same as main schema)
    #   o schema: (Required: if empty schema means valid schema, not required)
    #   o user: (NotRequired - Default same as main schema)
    #   o password: (NotRequired - Default same as main schema)
    #   o propertiesMap: (NotRequired - Default map:{})

    Set<DependencyScope> dependencyScopes();

    PathScope MAIN_COMPILE = pathScope(
            "main-compile",
            ProjectScope.MAIN,
            DependencyScope.COMPILE_ONLY,
            DependencyScope.COMPILE,
            DependencyScope.PROVIDED);

    PathScope MAIN_RUNTIME =
            pathScope("main-runtime", ProjectScope.MAIN, DependencyScope.COMPILE, DependencyScope.RUNTIME);

    PathScope TEST_COMPILE = pathScope(