The status codes in the 400 range mean that there was an error from the client.

Remember all those **"404 Not Found"** errors (and jokes)?

## Use `HTTPException`

To return HTTP responses with errors to the client you use `HTTPException`.

### Import `HTTPException`

```Python hl_lines="1"
{!../../docs_src/handling_errors/tutorial001.py!}
```

package jstream

import (
	"fmt"
	"strconv"
)

// Predefined errors
var (
	ErrSyntax        = DecoderError{msg: "invalid character"}
	ErrUnexpectedEOF = DecoderError{msg: "unexpected end of JSON input"}
	ErrMaxDepth      = DecoderError{msg: "maximum recursion depth exceeded"}
)

type errPos [2]int // line number, byte offset where error occurred

// DecoderError contains a detailed decoding error.
type DecoderError struct {

}

// toAPIErrorCode - Converts embedded errors. Convenience
// function written to handle all cases where we have known types of
// errors returned by underlying layers.
func toAPIErrorCode(ctx context.Context, err error) (apiErr APIErrorCode) {
	if err == nil {
		return ErrNone
	}

	// Errors that are generated by net.Conn and any context errors must be handled here.

```Python hl_lines="2  14-16"
{!../../docs_src/handling_errors/tutorial004.py!}
```

Wenn Sie nun `/items/foo` besuchen, erhalten Sie statt des Default-JSON-Errors:

```JSON
{
    "detail": [
        {
            "loc": [
                "path",
                "item_id"
            ],
            "msg": "value is not a valid integer",

Sebastián Ramírez <******@****.***> 1728247014 +0200

			configLogIf(ctx, fmt.Errorf("Unable to load drive config: %w", err))
		} else {
			if err = globalDriveConfig.Update(driveConfig); err != nil {
				configLogIf(ctx, fmt.Errorf("Unable to update drive config: %v", err))
			}
		}
	case config.BrowserSubSys:
		browserCfg, err := browser.LookupConfig(s[config.BrowserSubSys][config.Default])
		if err != nil {

				}
				jt.Take()
				go healEntry(bucket, *entry)
			},
			finished: func(errs []error) {
				if countErrs(errs, nil) != len(errs) {
					retErr = fmt.Errorf("one or more errors reported during listing: %v", errors.Join(errs...))
				}
			},
		})
		jt.Wait() // synchronize all the concurrent heal jobs
		if err != nil {
			// Set this such that when we return this function

		return errInvalidExpressionType(fmt.Errorf("invalid expression type '%v'", parsedS3Select.ExpressionType))
	}

	if parsedS3Select.Input.IsEmpty() {
		return errMissingRequiredParameter(fmt.Errorf("InputSerialization must be provided"))
	}

	if parsedS3Select.Output.IsEmpty() {
		return errMissingRequiredParameter(fmt.Errorf("OutputSerialization must be provided"))
	}

	if !a.Enable {
		return nil
	}
	if a.URL.IsEmpty() {
		return errors.New("empty URL")
	}
	if a.Format != "" {
		f := strings.ToLower(a.Format)
		if f != event.NamespaceFormat && f != event.AccessFormat {
			return errors.New("format value unrecognized")
		}
	}
	if a.Index == "" {
		return errors.New("empty index value")
	}

	if !w.Enable {
		return nil
	}
	if w.Endpoint.IsEmpty() {
		return errors.New("endpoint empty")
	}
	if w.QueueDir != "" {
		if !filepath.IsAbs(w.QueueDir) {
			return errors.New("queueDir path should be absolute")
		}
	}
	if w.ClientCert != "" && w.ClientKey == "" || w.ClientCert == "" && w.ClientKey != "" {
		return errors.New("cert and key must be specified as a pair")
	}
	return nil
}