Logging

Logging

Note

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.

Scrapy uses 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.

Logging works out of the box, and can be configured to some extent with the Scrapy settings listed in Logging settings.

Scrapy calls scrapy.utils.log.configure_logging() to set some reasonable defaults and handle those settings in Logging settings when running commands, so it’s recommended to manually call it if you’re running Scrapy from scripts as described in Run Scrapy from a script.

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:

logging.CRITICAL - for critical errors (highest severity)
logging.ERROR - for regular errors
logging.WARNING - for warning messages
logging.INFO - for informational messages
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")

Logging from Spiders

Scrapy provides a logger within each Spider instance, which can be accessed and used like this:

import scrapy
class MySpider(scrapy.Spider):
    name = 'myspider'
    start_urls = ['https://scrapinghub.com']
    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://scrapinghub.com']
    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 LOG_FILE is set, messages sent through the root logger will be redirected to a file named LOG_FILE with encoding LOG_ENCODING. If unset and LOG_ENABLED is True, log messages will be displayed on the standard error. Lastly, if LOG_ENABLED is False, there won’t be any visible log output.

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 Log levels.

LOG_FORMAT and LOG_DATEFORMAT specify formatting strings used as layouts for all messages. Those strings can contain any placeholders listed in logging’s logrecord attributes docs and datetime’s strftime and strptime directives respectively.

If 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.

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 LOG_FILE
--loglevel/-L LEVEL

Overrides LOG_LEVEL
--nolog

Sets LOG_ENABLED to False

Custom Log Formats

A custom log format can be set for different actions by extending LogFormatter class and making LOG_FORMATTER point to your new class.

class scrapy.logformatter.``LogFormatter[source]

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 : 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': u"Dropped: %(exception)s" + os.linesep + "%(item)s",
            'args': {
                'exception': exception,
                'item': item,
            }
        }

crawled(request, response, spider)[source]

Logs a message when the crawler finds a webpage.
download_error(failure, request, spider, errmsg=None)[source]

Logs a download error message from a spider (typically coming from the engine).

New in version 2.0.
dropped(item, exception, response, spider)[source]

Logs a message when an item is dropped while it is passing through the item pipeline.
item_error(item, exception, response, spider)[source]

Logs a message when an item causes an error while it is passing through the item pipeline.

New in version 2.0.
scraped(item, response, spider)[source]

Logs a message when an item is scraped by a spider.
spider_error(failure, request, response, spider)[source]

Logs an error message from a spider.

New in version 2.0.

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 LOG_SHORT_NAMES is likely set to True; set it to False and re-run the crawl.

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

scrapy.utils.log.``configure_logging(settings=None, install_root_handler=True)[source]

Initialize logging defaults for Scrapy.

Parameters
- settings (dict, Settings object or None) – settings used to create and configure a handler for the root logger (default: None).
- install_root_handler (bool) – whether to install root logging handler (default: True)

This function does:

Route warnings and twisted logging through Python standard logging
Assign DEBUG and ERROR level to Scrapy and Twisted loggers respectively
Route stdout to log if LOG_STDOUT setting is True

When install_root_handler is True (default), this function also creates a handler for the root logger according to given settings (see Logging settings). You can override default options using settings argument. When settings is empty or None, defaults are used.

configure_logging is automatically called when using Scrapy commands or CrawlerProcess, but needs to be called explicitly when running custom scripts using 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 logging.basicConfig() to set a basic root handler.

Note that CrawlerProcess automatically calls configure_logging, so it is recommended to only use logging.basicConfig() together with CrawlerRunner.

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

import logging
from scrapy.utils.log import configure_logging
logging.basicConfig(
    filename='log.txt',
    format='%(levelname)s: %(message)s',
    level=logging.INFO
)

Refer to Run Scrapy from a script for more details about using Scrapy this way.