# 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：

=== "Python 3.10+"

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

=== "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

### Importe `Query`

Para isso, primeiro importe `Query` de `fastapi`:

```Python hl_lines="3"
{!../../../docs_src/query_params_str_validations/tutorial002.py!}
```

## Use `Query` como o valor padrão

Agora utilize-o como valor padrão do seu parâmetro, definindo o parâmetro `max_length` para 50:

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

=== "Python 3.10+"

    ```Python hl_lines="1"
    {!> ../../../docs_src/python_types/tutorial009_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="1  4"
    {!> ../../../docs_src/python_types/tutorial009.py!}
    ```

=== "Python 3.8+ alternative"

    ```Python hl_lines="1  4"
    {!> ../../../docs_src/python_types/tutorial009b.py!}
    ```

    E.g. `pip install python-multipart`.

## Import `File` and `Form`

=== "Python 3.9+"

    ```Python hl_lines="3"
    {!> ../../../docs_src/request_forms_and_files/tutorial001_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="1"
    {!> ../../../docs_src/request_forms_and_files/tutorial001_an.py!}
    ```

=== "Python 3.8+ non-Annotated"

    !!! tip

```

:

=== "🐍 3️⃣.6️⃣ & 🔛"

    ```Python hl_lines="17"
    {!> ../../../docs_src/body_multiple_params/tutorial005.py!}
    ```

=== "🐍 3️⃣.1️⃣0️⃣ & 🔛"

    ```Python hl_lines="15"
    {!> ../../../docs_src/body_multiple_params/tutorial005_py310.py!}
    ```

👉 💼 **FastAPI** 🔜 ⌛ 💪 💖:

```JSON hl_lines="2"
{
    "item": {
        "name": "Foo",

=== "Python 3.10+"

    ```Python hl_lines="68-69  82"
    {!> ../../../docs_src/websockets/tutorial002_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="68-69  82"
    {!> ../../../docs_src/websockets/tutorial002_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="69-70  83"
    {!> ../../../docs_src/websockets/tutorial002_an.py!}
    ```

=== "Python 3.10+"

    ```Python hl_lines="13  15  22  25"
    {!> ../../../docs_src/background_tasks/tutorial002_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="13  15  22  25"
    {!> ../../../docs_src/background_tasks/tutorial002_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="14  16  23  26"
    {!> ../../../docs_src/background_tasks/tutorial002_an.py!}

Sie können FastAPI auf GitHub „starren“ (durch Klicken auf den Stern-Button oben rechts): <a href="https://github.com/tiangolo/fastapi" class="external-link" target="_blank">https://github.com/tiangolo/fastapi</a>. ⭐️

Durch das Hinzufügen eines Sterns können andere Benutzer es leichter finden und sehen, dass es für andere bereits nützlich war.

## Das GitHub-Repository auf Releases beobachten

=== "Python 3.9+"

    ```Python hl_lines="7  14"
    {!> ../../../docs_src/request_files/tutorial001_02_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="9  17"
    {!> ../../../docs_src/request_files/tutorial001_02.py!}
    ```

## 带有额外元数据的 `UploadFile`

您也可以将 `File()` 与 `UploadFile` 一起使用，例如，设置额外的元数据:

```Python hl_lines="13"
{!../../../docs_src/request_files/tutorial001_03.py!}

For now, don't pay attention to the rest, only the imports:

```Python hl_lines="3-5"
{!../../../docs_src/nosql_databases/tutorial001.py!}
```

## Define a constant to use as a "document type"

We will use it later as a fixed field `type` in our documents.

This is not required by Couchbase, but is a good practice that will help you afterwards.

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