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Coloured terminal output for Python's logging module

Project description

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:

https://colouredlogs.readthedocs.io/en/latest/_images/defaults.png

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).

Installation

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 ;-).

Usage

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")

Format of log messages

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[30462] DEBUG message with level 'debug'
2015-10-23 03:32:23 peter-macbook colouredlogs.demo[30462] VERBOSE message with level 'verbose'
2015-10-23 03:32:24 peter-macbook colouredlogs.demo[30462] 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.

Enabling millisecond precision

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:

  1. The easy way is to pass the milliseconds argument to colouredlogs.install():

    colouredlogs.install(milliseconds=True)
    

    This became supported in release 7.1 (due to #16).

  2. 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.

  3. 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).

Coloured output from cron

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:

Modifying your crontab

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 :-)

Modifying your Python code

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 :-).

Contact

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 peter@peterodding.com.

License

This software is licensed under the MIT license.

© 2018 Peter Odding.

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