//// tab | Python 3.9+

```Python hl_lines="3  6-8" title="app/dependencies.py"
{!> ../../docs_src/bigger_applications/app_an_py39/dependencies.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="1  5-7" title="app/dependencies.py"
{!> ../../docs_src/bigger_applications/app_an/dependencies.py!}
```

////

//// tab | Python 3.8+ non-Annotated

    * You can normally quickly detect it by going to the "Files changed" tab in the PR and checking if the updated file(s) starts with `docs/en/docs`. The original version of the docs is always in English, so in `docs/en/docs`.
* `lang-all`: Translations

//// tab | Python 3.9+

```Python hl_lines="3  6-8" title="app/dependencies.py"
{!> ../../docs_src/bigger_applications/app_an_py39/dependencies.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="1  5-7" title="app/dependencies.py"
{!> ../../docs_src/bigger_applications/app_an/dependencies.py!}
```

////

//// tab | Python 3.8+ nicht annotiert

👆 💪 ✍ & ⚙️ 🌐 🔢 🐚, 🍵 💆‍♂ 🐍:

//// tab | 💾, 🇸🇻, 🚪 🎉

<div class="termy">

```console
// You could create an env var MY_NAME with
$ export MY_NAME="Wade Wilson"

// Then you could use it with other programs, like
$ echo "Hello $MY_NAME"

Hello Wade Wilson
```

</div>

////

//// tab | 🚪 📋

<div class="termy">

```console

# 查询参数和字符串校验

**FastAPI** 允许你为参数声明额外的信息和校验。

让我们以下面的应用程序为例：

//// tab | Python 3.10+

```Python hl_lines="7"
{!> ../../docs_src/query_params_str_validations/tutorial001_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="9"
{!> ../../docs_src/query_params_str_validations/tutorial001.py!}
```

////

查询参数 `q` 的类型为 `str`，默认值为 `None`，因此它是可选的。

## 额外的校验

  /**
   * <a href="http://www.iana.org/assignments/media-types/text/tab-separated-values">Tab separated
   * values</a>.
   *
   * @since 15.0
   */
  public static final MediaType TSV_UTF_8 = createConstantUtf8(TEXT_TYPE, "tab-separated-values");

  public static final MediaType VCARD_UTF_8 = createConstantUtf8(TEXT_TYPE, "vcard");

  /**

   * the XML specification.
   *
   * <p>This escaper does not escape non-ASCII characters to their numeric character references
   * (NCR). However, horizontal tab {@code '\t'}, line feed {@code '\n'} and carriage return {@code
   * '\r'} are escaped to a corresponding NCR {@code "&#x9;"}, {@code "&#xA;"}, and {@code "&#xD;"}

.nav-item`\nconst SELECTOR_TAB_NAVBAR_NAV_LINK = `${SELECTOR_TAB_NAVBAR_NAV} .nav-link`\nconst SELECTOR_TAB_CONTENT = `${SELECTOR_CONTENT_WRAPPER}.iframe-mode .tab-content`\nconst SELECTOR_TAB_EMPTY = `${SELECTOR_TAB_CONTENT} .tab-empty`\nconst SELECTOR_TAB_LOADING = `${SELECTOR_TAB_CONTENT} .tab-loading`\nconst SELECTOR_TAB_PANE = `${SELECTOR_TAB_CONTENT} .tab-pane`\nconst SELECTOR_SIDEBAR_MENU_ITEM = '.main-sidebar .nav-item > a.nav-link'\nconst SELECTOR_SIDEBAR_SEARCH_ITEM = '.sidebar-search-results .lis...

*/\n\n$(document)\n  .on(EVENT_CLICK_DATA_API, SELECTOR_DATA_TOGGLE, function (event) {\n    event.preventDefault()\n    Tab._jQueryInterface.call($(this), 'show')\n  })\n\n/**\n * jQuery\n */\n\n$.fn[NAME] = Tab._jQueryInterface\n$.fn[NAME].Constructor = Tab\n$.fn[NAME].noConflict = () => {\n  $.fn[NAME] = JQUERY_NO_CONFLICT\n  return Tab._jQueryInterface\n}\n\nexport default Tab\n","/**\n * --------------------------------------------------------------------------\n * Bootstrap (v4.6.2): toast.js\n...

    }

    /**
     * <p>Escapes the characters in a <code>String</code> using Java String rules.</p>
     *
     * <p>Deals correctly with quotes and control-chars (tab, backslash, cr, ff, etc.) </p>
     *
     * <p>So a tab becomes the characters <code>'\\'</code> and
     * <code>'t'</code>.</p>
     *
     * <p>The only difference between Java strings and JavaScript strings