# Default options should come above this line.

# Android configs. Bazel needs to have --cpu and --fat_apk_cpu both set to the
# target CPU to build transient dependencies correctly. See
# https://docs.bazel.build/versions/master/user-manual.html#flag--fat_apk_cpu
common:android --config=clang_local
common:android --crosstool_top=//external:android/crosstool
common:android --host_crosstool_top=@bazel_tools//tools/cpp:toolchain

```Python hl_lines="3"
import os

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

/// tip | Consejo

El segundo argumento de <a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> es el valor por defecto a retornar.

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package gradlebuild.docs;

import com.google.common.io.CharStreams;
import org.gradle.api.GradleException;
import org.gradle.internal.UncheckedException;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;

		return
	}

	// Content-Md5 is required should be set
	// http://docs.aws.amazon.com/AmazonS3/latest/API/multiobjectdeleteapi.html
	if !validateLengthAndChecksum(r) {
		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrMissingContentMD5), r.URL)
		return
	}

	// Content-Length is required and should be non-zero
	// http://docs.aws.amazon.com/AmazonS3/latest/API/multiobjectdeleteapi.html
	if r.ContentLength <= 0 {

Abgesehen von normalen einfachen Typen wie `str`, `int`, `float`, usw. können Sie komplexere einfache Typen verwenden, die von `str` erben.

Um alle Optionen kennenzulernen, die Sie haben, schauen Sie sich <a href="https://docs.pydantic.dev/latest/concepts/types/" class="external-link" target="_blank">Pydantics Typübersicht</a> an. Sie werden einige Beispiele im nächsten Kapitel kennenlernen.

它基于 <a href="https://www.python-httpx.org" class="external-link" target="_blank">HTTPX</a>， 而HTTPX又是基于Requests设计的，所以很相似且易懂。

有了它，你可以直接与**FastAPI**一起使用 <a href="https://docs.pytest.org/" class="external-link" target="_blank">pytest</a>。

## 使用 `TestClient`

/// info | 信息

要使用 `TestClient`，先要安装 <a href="https://www.python-httpx.org" class="external-link" target="_blank">`httpx`</a>.

您可以运行这个应用程序：

<div class="termy">

```console
$ fastapi dev main.py

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

</div>

然后在 `/docs` UI 中，您能够看到 **FastAPI** 会用这些**模型**来**记录** API，并且还会用它们来**序列化**和**验证**数据。

<div class="screenshot">
<img src="/img/tutorial/sql-databases/image01.png">
</div>

## 更新应用程序以支持多个模型

func (db *DB) Update(column string, value interface{}) (tx *DB) {
	tx = db.getInstance()
	tx.Statement.Dest = map[string]interface{}{column: value}
	return tx.callbacks.Update().Execute(tx)
}

// Updates updates attributes using callbacks. values must be a struct or map. Reference: https://gorm.io/docs/update.html#Update-Changed-Fields

```console
$ fastapi dev main.py

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

</div>

Então, vá para a interface `/docs`, você verá que o **FastAPI** está usando esses **modelos** para **documentar** a API, e ele também os usará para **serializar** e **validar** os dados.

<div class="screenshot">
<img src="/img/tutorial/sql-databases/image01.png">

```

### `RequestValidationError` vs `ValidationError`

/// warning | 警告

如果您觉得现在还用不到以下技术细节，可以先跳过下面的内容。

///

`RequestValidationError` 是 Pydantic 的 <a href="https://docs.pydantic.dev/latest/concepts/models/#error-handling" class="external-link" target="_blank">`ValidationError`</a> 的子类。

**FastAPI** 调用的就是 `RequestValidationError` 类，因此，如果在 `response_model` 中使用 Pydantic 模型，且数据有错误时，在日志中就会看到这个错误。