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 Python’s builtin logging system 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

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.