Class HTTPError

python/python3/tornado/web.py:2368–2413

An exception that will turn into an HTTP error response. Raising an `HTTPError` is a convenient alternative to calling `RequestHandler.send_error` since it automatically ends the current function. To customize the response sent with an `HTTPError`, override `RequestHandler.writ

class HTTPError(Exception):
    """An exception that will turn into an HTTP error response.

    Raising an `HTTPError` is a convenient alternative to calling
    `RequestHandler.send_error` since it automatically ends the
    current function.

    To customize the response sent with an `HTTPError`, override
    `RequestHandler.write_error`.

    :arg int status_code: HTTP status code.  Must be listed in
        `httplib.responses <http.client.responses>` unless the ``reason``
        keyword argument is given.
    :arg str log_message: Message to be written to the log for this error
        (will not be shown to the user unless the `Application` is in debug
        mode).  May contain ``%s``-style placeholders, which will be filled
        in with remaining positional parameters.
    :arg str reason: Keyword-only argument.  The HTTP "reason" phrase
        to pass in the status line along with ``status_code``.  Normally
        determined automatically from ``status_code``, but can be used
        to use a non-standard numeric code.
    """

    def __init__(
        self,
        status_code: int = 500,
        log_message: Optional[str] = None,
        *args: Any,
        **kwargs: Any
    ) -> None:
        self.status_code = status_code
        self.log_message = log_message
        self.args = args
        self.reason = kwargs.get("reason", None)
        if log_message and not args:
            self.log_message = log_message.replace("%", "%%")

    def __str__(self) -> str:
        message = "HTTP %d: %s" % (
            self.status_code,
            self.reason or httputil.responses.get(self.status_code, "Unknown"),
        )
        if self.log_message:
            return message + " (" + (self.log_message % self.args) + ")"
        else:
            return message


class Finish(Exception):