Coloured terminal output for Python's logging module
NOTE: This is a parody of the great python-colouredlogs project by Peter Odding. Please use that package as I currently have no plans to maintain this one. All I’ve done is s/color/colour/g.
The colouredlogs package enables coloured terminal output for Python’s logging module. The ColouredFormatter class inherits from logging.Formatter and uses ANSI escape sequences to render your logging messages in colour. It uses only standard colours so it should work on any UNIX terminal. It’s currently tested on Python 2.6, 2.7, 3.4, 3.5, 3.6 and PyPy. On Windows colouredlogs automatically pulls in Colourama as a dependency and enables ANSI escape sequence translation using Colourama. Here is a screen shot of the demo that is printed when the command colouredlogs --demo is executed:
Note that the screenshot above includes custom logging levels defined by my verboselogs package: if you install both colouredlogs and verboselogs it will Just Work (verboselogs is of course not required to use colouredlogs).
The colouredlogs package is available on PyPI which means installation should be as simple as:
$ pip install colouredlogs
There’s actually a multitude of ways to install Python packages (e.g. the per user site-packages directory, virtual environments or just installing system wide) and I have no intention of getting into that discussion here, so if this intimidates you then read up on your options before returning to these instructions ;-).
Here’s an example of how easy it is to get started:
import colouredlogs, logging # Create a logger object. logger = logging.getLogger(__name__) # By default the install() function installs a handler on the root logger, # this means that log messages from your code and log messages from the # libraries that you use will all show up on the terminal. colouredlogs.install(level='DEBUG') # If you don't want to see log messages from libraries, you can pass a # specific logger object to the install() function. In this case only log # messages originating from that logger will show up on the terminal. colouredlogs.install(level='DEBUG', logger=logger) # Some examples. logger.debug("this is a debugging message") logger.info("this is an informational message") logger.warning("this is a warning message") logger.error("this is an error message") logger.critical("this is a critical message")
The ColouredFormatter class supports user defined log formats so you can use any log format you like. The default log format is as follows:
%(asctime)s %(hostname)s %(name)s[%(process)d] %(levelname)s %(message)s
This log format results in the following output:
2015-10-23 03:32:22 peter-macbook colouredlogs.demo DEBUG message with level 'debug' 2015-10-23 03:32:23 peter-macbook colouredlogs.demo VERBOSE message with level 'verbose' 2015-10-23 03:32:24 peter-macbook colouredlogs.demo INFO message with level 'info' ...
You can customize the log format and styling using environment variables as well as programmatically, please refer to the online documentation for details.
If you’re switching from logging.basicConfig() to colouredlogs.install() you may notice that timestamps no longer include milliseconds. This is because colouredlogs doesn’t output milliseconds in timestamps unless you explicitly tell it to. There are three ways to do that:
The easy way is to pass the milliseconds argument to colouredlogs.install():
Alternatively you can change the log format to include ‘msecs’:
%(asctime)s,%(msecs)03d %(hostname)s %(name)s[%(process)d] %(levelname)s %(message)s
Here’s what the call to colouredlogs.install() would then look like:
colouredlogs.install(fmt='%(asctime)s,%(msecs)03d %(hostname)s %(name)s[%(process)d] %(levelname)s %(message)s')
Customizing the log format also enables you to change the delimiter that separates seconds from milliseconds (the comma above). This became possible in release 3.0 which added support for user defined log formats.
If the use of %(msecs)d isn’t flexible enough you can instead add %f to the date/time format, it will be replaced by the value of %(msecs)03d. Support for the %f directive was added to release 9.3 (due to #45).
The online documentation contains an example of customizing the text styles and colours.
When colouredlogs is used in a cron job, the output that’s e-mailed to you by cron won’t contain any ANSI escape sequences because colouredlogs realizes that it’s not attached to an interactive terminal. If you’d like to have colours e-mailed to you by cron there are two ways to make it happen:
Here’s an example of a minimal crontab:
MAILTO="your-email-address@here" CONTENT_TYPE="text/html" * * * * * root colouredlogs --to-html your-command
The colouredlogs program is installed when you install the colouredlogs Python package. When you execute colouredlogs --to-html your-command it runs your-command under the external program script (you need to have this installed). This makes your-command think that it’s attached to an interactive terminal which means it will output ANSI escape sequences which will then be converted to HTML by the colouredlogs program. Yes, this is a bit convoluted, but it works great :-)
The ColouredCronMailer class provides a context manager that automatically enables HTML output when the $CONTENT_TYPE variable has been correctly set in the crontab.
This requires my capturer package which you can install using pip install 'colouredlogs[cron]'. The [cron] extra will pull in capturer 2.4 or newer which is required to capture the output while silencing it - otherwise you’d get duplicate output in the emails sent by cron.
The context manager can also be used to retroactively silence output that has already been produced, this can be useful to avoid spammy cron jobs that have nothing useful to do but still email their output to the system administrator every few minutes :-).
The latest version of colouredlogs is available on PyPI and GitHub. The online documentation is available on Read The Docs and includes a changelog. For bug reports please create an issue on GitHub. If you have questions, suggestions, etc. feel free to send me an e-mail at firstname.lastname@example.org.
This software is licensed under the MIT license.
© 2018 Peter Odding.
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