例えば、以下のような`main.py`ファイルを用意します:

```Python hl_lines="3"
import os

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

/// tip | 豆知識

[`os.getenv()`](https://docs.python.org/3.8/library/os.html#os.getenv) の第2引数は、返されるデフォルト値です。

指定しない場合、デフォルトは`None`ですが、ここでは使用するデフォルト値として`"World"`を指定しています。

///

次に、このPythonプログラムを呼び出します。

//// tab | Linux, macOS, Windows Bash

<div class="termy">

controlled by the [`x509usefallbackroots` setting](/pkg/crypto/x509/#SetFallbackRoots).

Go 1.20 removed the preinstalled `.a` files for the standard library
from the Go distribution.
Installations now build and cache the standard library like
packages in other modules.
The [`installgoroot` setting](/cmd/go#hdr-Compile_and_install_packages_and_dependencies)
restores the installation and use of preinstalled `.a` files.

例如，你可以建立一個名為 `main.py` 的檔案，其中包含以下內容：

```Python hl_lines="3"
import os

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

/// tip

第二個參數是 [`os.getenv()`](https://docs.python.org/3.8/library/os.html#os.getenv) 的預設回傳值。

如果沒有提供，預設值為 `None`，這裡我們提供 `"World"` 作為預設值。

///

然後你可以呼叫這個 Python 程式：

//// tab | Linux, macOS, Windows Bash

<div class="termy">

```console
// 這裡我們還沒有設定環境變數

   * is defined as the function h such that {@code h(a) == g(f(a))} for each {@code a}.
   *
   * <p><b>JRE users and Android users who opt in to library desugaring:</b> use {@code
   * g.compose(f)} or (probably clearer) {@code f.andThen(g)} instead. Note that it is not
   * serializable.
   *
   * @param g the second function to apply

   * identically to this equivalence.
   *
   * <p><b>Warning: do not depend</b> on the behavior of this method.
   *
   * <p>Historically, {@code Equivalence} instances in this library have implemented this method to
   * recognize certain cases where distinct {@code Equivalence} instances would in fact behave
   * identically. However, as code migrates to {@code java.util.function}, that behavior will

// all the way up to GOMAXPROCS.
var listSem = make(chan semToken, 2)

type semToken struct{}

// loadImports populates w with information about the packages in the standard
// library and the packages they themselves import in w's build context.
//
// The source import path and expanded import path are identical except for vendored packages.
// For example, on return:
//

 * implementations in Java use). For the many uses of hash functions beyond data structures,
 * however, {@code Object.hashCode} almost always falls short -- hence this library.
 *
 * @author Kevin Bourrillion
 * @since 11.0
 */
@Immutable
public interface HashFunction {
  /**
   * Begins a new hash code computation by returning an initialized, stateful {@code Hasher}

在我們的相依 `get_settings()` 這個案例中，該函式甚至不帶任何參數，因此它總是回傳相同的值。

如此一來，它的行為幾乎就像全域變數。但因為它使用相依函式，因此我們可以在測試時輕鬆將其覆寫。

`@lru_cache` 是 `functools` 的一部分，而 `functools` 是 Python 標準程式庫的一部分。你可以在[Python 文件中閱讀 `@lru_cache`](https://docs.python.org/3/library/functools.html#functools.lru_cache) 以了解更多。

## 回顧 { #recap }

你可以使用 Pydantic Settings 來處理應用程式的設定或組態，並享有 Pydantic model 的全部能力。

- 透過相依可以讓測試更容易。
- 你可以搭配 `.env` 檔使用。

		</dependency>
		<dependency>
			<groupId>org.ow2.asm</groupId>
			<artifactId>asm-util</artifactId>
			<version>${asm.version}</version>
		</dependency>

		<!-- common library -->
		<dependency>
			<groupId>com.google.guava</groupId>
			<artifactId>guava</artifactId>
			<version>${guava.version}</version>
			<exclusions>
				<exclusion>

* the code
* the commit
* the context manager
* the coroutine
* the database session
* the disk
* the domain
* the engine
* the fake X
* the HTTP GET method
* the item
* the library
* the lifespan
* the lock
* the middleware
* the mobile application
* the module
* the mounting
* the network
* the origin
* the override
* the payload
* the processor
* the property