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Logging

Note

:mod:`scrapy.log` has been deprecated alongside its functions in favor of explicit calls to the Python standard logging. Keep reading to learn more about the new logging system.

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Scrapy uses :mod:`logging` for event logging. We'll provide some simple examples to get you started, but for more advanced use-cases it's strongly suggested to read thoroughly its documentation.

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Logging works out of the box, and can be configured to some extent with the Scrapy settings listed in :ref:`topics-logging-settings`.

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Scrapy calls :func:`scrapy.utils.log.configure_logging` to set some reasonable defaults and handle those settings in :ref:`topics-logging-settings` when running commands, so it's recommended to manually call it if you're running Scrapy from scripts as described in :ref:`run-from-script`.

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Log levels

Python's builtin logging defines 5 different levels to indicate the severity of a given log message. Here are the standard ones, listed in decreasing order:

  1. logging.CRITICAL - for critical errors (highest severity)
  2. logging.ERROR - for regular errors
  3. logging.WARNING - for warning messages
  4. logging.INFO - for informational messages
  5. logging.DEBUG - for debugging messages (lowest severity)

How to log messages

Here's a quick example of how to log a message using the logging.WARNING level:

import logging
logging.warning("This is a warning")

There are shortcuts for issuing log messages on any of the standard 5 levels, and there's also a general logging.log method which takes a given level as argument. If needed, the last example could be rewritten as:

import logging
logging.log(logging.WARNING, "This is a warning")

On top of that, you can create different "loggers" to encapsulate messages. (For example, a common practice is to create different loggers for every module). These loggers can be configured independently, and they allow hierarchical constructions.

The previous examples use the root logger behind the scenes, which is a top level logger where all messages are propagated to (unless otherwise specified). Using logging helpers is merely a shortcut for getting the root logger explicitly, so this is also an equivalent of the last snippets:

import logging
logger = logging.getLogger()
logger.warning("This is a warning")

You can use a different logger just by getting its name with the logging.getLogger function:

import logging
logger = logging.getLogger('mycustomlogger')
logger.warning("This is a warning")

Finally, you can ensure having a custom logger for any module you're working on by using the __name__ variable, which is populated with current module's path:

import logging
logger = logging.getLogger(__name__)
logger.warning("This is a warning")

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.. seealso::

    Module logging, :doc:`HowTo <howto/logging>`
        Basic Logging Tutorial

    Module logging, :ref:`Loggers <logger>`
        Further documentation on loggers

Logging from Spiders

Scrapy provides a :data:`~scrapy.spiders.Spider.logger` within each Spider instance, which can be accessed and used like this:

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import scrapy

class MySpider(scrapy.Spider):

    name = 'myspider'
    start_urls = ['https://scrapy.org']

    def parse(self, response):
        self.logger.info('Parse function called on %s', response.url)

That logger is created using the Spider's name, but you can use any custom Python logger you want. For example:

import logging
import scrapy

logger = logging.getLogger('mycustomlogger')

class MySpider(scrapy.Spider):

    name = 'myspider'
    start_urls = ['https://scrapy.org']

    def parse(self, response):
        logger.info('Parse function called on %s', response.url)

Logging configuration

Loggers on their own don't manage how messages sent through them are displayed. For this task, different "handlers" can be attached to any logger instance and they will redirect those messages to appropriate destinations, such as the standard output, files, emails, etc.

By default, Scrapy sets and configures a handler for the root logger, based on the settings below.

Logging settings

These settings can be used to configure the logging:

The first couple of settings define a destination for log messages. If :setting:`LOG_FILE` is set, messages sent through the root logger will be redirected to a file named :setting:`LOG_FILE` with encoding :setting:`LOG_ENCODING`. If unset and :setting:`LOG_ENABLED` is True, log messages will be displayed on the standard error. Lastly, if :setting:`LOG_ENABLED` is False, there won't be any visible log output.

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:setting:`LOG_LEVEL` determines the minimum level of severity to display, those messages with lower severity will be filtered out. It ranges through the possible levels listed in :ref:`topics-logging-levels`.

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:setting:`LOG_FORMAT` and :setting:`LOG_DATEFORMAT` specify formatting strings used as layouts for all messages. Those strings can contain any placeholders listed in :ref:`logging's logrecord attributes docs <logrecord-attributes>` and :ref:`datetime's strftime and strptime directives <strftime-strptime-behavior>` respectively.

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If :setting:`LOG_SHORT_NAMES` is set, then the logs will not display the Scrapy component that prints the log. It is unset by default, hence logs contain the Scrapy component responsible for that log output.

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Command-line options

There are command-line arguments, available for all commands, that you can use to override some of the Scrapy settings regarding logging.

  • --logfile FILE

    Overrides :setting:`LOG_FILE`

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  • --loglevel/-L LEVEL

    Overrides :setting:`LOG_LEVEL`

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  • --nolog

    Sets :setting:`LOG_ENABLED` to False

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.. seealso::

    Module :mod:`logging.handlers`
        Further documentation on available handlers

Custom Log Formats

A custom log format can be set for different actions by extending :class:`~scrapy.logformatter.LogFormatter` class and making :setting:`LOG_FORMATTER` point to your new class.

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.. autoclass:: scrapy.logformatter.LogFormatter
   :members:

Advanced customization

Because Scrapy uses stdlib logging module, you can customize logging using all features of stdlib logging.

For example, let's say you're scraping a website which returns many HTTP 404 and 500 responses, and you want to hide all messages like this:

2016-12-16 22:00:06 [scrapy.spidermiddlewares.httperror] INFO: Ignoring
response <500 http://quotes.toscrape.com/page/1-34/>: HTTP status code
is not handled or not allowed

The first thing to note is a logger name - it is in brackets: [scrapy.spidermiddlewares.httperror]. If you get just [scrapy] then :setting:`LOG_SHORT_NAMES` is likely set to True; set it to False and re-run the crawl.

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Next, we can see that the message has INFO level. To hide it we should set logging level for scrapy.spidermiddlewares.httperror higher than INFO; next level after INFO is WARNING. It could be done e.g. in the spider's __init__ method:

import logging
import scrapy


class MySpider(scrapy.Spider):
    # ...
    def __init__(self, *args, **kwargs):
        logger = logging.getLogger('scrapy.spidermiddlewares.httperror')
        logger.setLevel(logging.WARNING)
        super().__init__(*args, **kwargs)

If you run this spider again then INFO messages from scrapy.spidermiddlewares.httperror logger will be gone.

scrapy.utils.log module

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.. module:: scrapy.utils.log
   :synopsis: Logging utils

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.. autofunction:: configure_logging

    ``configure_logging`` is automatically called when using Scrapy commands
    or :class:`~scrapy.crawler.CrawlerProcess`, but needs to be called explicitly
    when running custom scripts using :class:`~scrapy.crawler.CrawlerRunner`.
    In that case, its usage is not required but it's recommended.

    Another option when running custom scripts is to manually configure the logging.
    To do this you can use :func:`logging.basicConfig` to set a basic root handler.

    Note that :class:`~scrapy.crawler.CrawlerProcess` automatically calls ``configure_logging``,
    so it is recommended to only use :func:`logging.basicConfig` together with
    :class:`~scrapy.crawler.CrawlerRunner`.

    This is an example on how to redirect ``INFO`` or higher messages to a file::

        import logging

        logging.basicConfig(
            filename='log.txt',
            format='%(levelname)s: %(message)s',
            level=logging.INFO
        )

    Refer to :ref:`run-from-script` for more details about using Scrapy this
    way.
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