```Python hl_lines="9"
{!../../../docs_src/query_params_str_validations/tutorial003.py!}
```

## Ajouter des validations par expressions régulières

On peut définir une <abbr title="Une expression régulière, regex ou regexp est une suite de caractères qui définit un pattern de correspondance pour les chaînes de caractères.">expression régulière</abbr> à laquelle le paramètre doit correspondre :

```Python hl_lines="10"

* Der *Pfad* kann einen <a href="https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.1.0.md#key-expression" class="external-link" target="_blank">OpenAPI-3-Ausdruck</a> enthalten (mehr dazu weiter unten), wo er Variablen mit Parametern und Teilen des ursprünglichen Requests verwenden kann, der an *Ihre API* gesendet wurde.

*  *➡* 💪 🔌 <a href="https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#key-expression" class="external-link" target="_blank">🗄 3️⃣ 🧬</a> (👀 🌖 🔛) 🌐❔ ⚫️ 💪 ⚙️ 🔢 ⏮️ 🔢 &amp; 🍕 ⏮️ 📨 📨 *👆 🛠️*.

### ⏲ ➡ 🧬

⏲ *➡* 💪 ✔️ <a href="https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#key-expression" class="external-link" target="_blank">🗄 3️⃣ 🧬</a> 👈 💪 🔌 🍕 ⏮️ 📨 📨 *👆 🛠️*.

👉 💼, ⚫️ `str`:

### The callback path expression

(if a <code>license_info</code> is set). The license name used for the API.</td></tr><tr><td><code>identifier</code></td><td><code>str</code></td><td>An <a href="https://spdx.org/licenses/" class="external-link" target="_blank">SPDX</a> license expression for the API. The <code>identifier</code> field is mutually exclusive of the <code>url</code> field. <small>Available since OpenAPI 3.1.0, FastAPI 0.99.0.</small></td></tr><tr><td><code>url</code></td><td><code>str</code></td><td>A URL to the license...

=== "🐍 3️⃣.1️⃣0️⃣ & 🔛"

    ```Python hl_lines="7"
    {!> ../../../docs_src/query_params_str_validations/tutorial003_py310.py!}
    ```

## 🚮 🥔 🧬

👆 💪 🔬 <abbr title="A regular expression, regex or regexp is a sequence of characters that define a search pattern for strings.">🥔 🧬</abbr> 👈 🔢 🔜 🏏:

=== "🐍 3️⃣.6️⃣ &amp; 🔛"

    ```Python hl_lines="11"

* *路径*可以包含 <a href="https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#key-expression" class="external-link" target="_blank">OpenAPI 3 表达式</a>（详见下文），可以使用带参数的变量，以及发送至您的 API 的原始请求的部分

### 回调路径表达式

回调*路径*支持包含发送给您的 API 的原始请求的部分的  <a href="https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#key-expression" class="external-link" target="_blank">OpenAPI 3 表达式</a>。

本例中是**字符串**：

```Python

    ```Python hl_lines="10"
    {!> ../../../docs_src/query_params_str_validations/tutorial003.py!}
    ```

## Add regular expressions

You can define a <abbr title="A regular expression, regex or regexp is a sequence of characters that define a search pattern for strings.">regular expression</abbr> `pattern` that the parameter should match:

=== "Python 3.10+"

    ```Python hl_lines="11"

    ```

## Description from docstring

As descriptions tend to be long and cover multiple lines, you can declare the *path operation* description in the function <abbr title="a multi-line string as the first expression inside a function (not assigned to any variable) used for documentation">docstring</abbr> and **FastAPI** will read it from there.

Create functions with a name that starts with `test_` (this is standard `pytest` conventions).

Use the `TestClient` object the same way as you do with `httpx`.

Write simple `assert` statements with the standard Python expressions that you need to check (again, standard `pytest`).

```Python hl_lines="2  12  15-18"
{!../../../docs_src/app_testing/tutorial001.py!}
```

!!! tip