Class LogFormatter

scrapy/logformatter.py:37–195

Class for generating log messages for different actions. All methods must return a dictionary listing the parameters ``level``, ``msg`` and ``args`` which are going to be used for constructing the log message when calling ``logging.log``. Dictionary keys for the method outputs:

class LogFormatter:
    """Class for generating log messages for different actions.

    All methods must return a dictionary listing the parameters ``level``, ``msg``
    and ``args`` which are going to be used for constructing the log message when
    calling ``logging.log``.

    Dictionary keys for the method outputs:

    *   ``level`` is the log level for that action, you can use those from the
        `python logging library <https://docs.python.org/3/library/logging.html>`_ :
        ``logging.DEBUG``, ``logging.INFO``, ``logging.WARNING``, ``logging.ERROR``
        and ``logging.CRITICAL``.
    *   ``msg`` should be a string that can contain different formatting placeholders.
        This string, formatted with the provided ``args``, is going to be the long message
        for that action.
    *   ``args`` should be a tuple or dict with the formatting placeholders for ``msg``.
        The final log message is computed as ``msg % args``.

    Users can define their own ``LogFormatter`` class if they want to customize how
    each action is logged or if they want to omit it entirely. In order to omit
    logging an action the method must return ``None``.

    Here is an example on how to create a custom log formatter to lower the severity level of
    the log message when an item is dropped from the pipeline::

            class PoliteLogFormatter(logformatter.LogFormatter):
                def dropped(self, item, exception, response, spider):
                    return {
                        'level': logging.INFO, # lowering the level from logging.WARNING
                        'msg': "Dropped: %(exception)s" + os.linesep + "%(item)s",
                        'args': {
                            'exception': exception,
                            'item': item,
                        }
                    }
    """

    def crawled(
        self, request: Request, response: Response, spider: Spider
    ) -> LogFormatterResult:
        """Logs a message when the crawler finds a webpage."""
        request_flags = f" {request.flags!s}" if request.flags else ""
        response_flags = f" {response.flags!s}" if response.flags else ""
        return {
            "level": logging.DEBUG,
            "msg": CRAWLEDMSG,
            "args": {
                "status": response.status,
                "request": request,
                "request_flags": request_flags,
                "referer": referer_str(request),
                "response_flags": response_flags,
                # backward compatibility with Scrapy logformatter below 1.4 version
                "flags": response_flags,
            },
        }