savoirfairelinux/colorlogging

Simple color logging for Python.

colorlogging

Colorful Python logging for Linux shells.

Table of Contents

• Requirements
• Installation
• Example
• Colors and Styles
• Options
• Todo

Requirements

Python 2.7+ (Python 3 supported).

No additional requirements.

Installation

This package is not (yet?) on pypi. To install:

git clone https://github.com/jbchouinard/colorlogging.git
cd colorlogging
pip install .

Example

colorlogging has a single class, ColorFormatter.

import logging
from colorlogging import ColorFormatter

logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
handler = logging.StreamHandler()
logger.addHandler(handler)

fmt = "%(asctime)s %(levelname)s: #(magenta)%(message)s"
formatter = ColorFormatter(fmt)
handler.setFormatter(formatter)

logger.info('This will be printed in magenta!')

Format strings are handled as usual (see the Formatter documentation, py2, py3), with one addition:

Style modifiers like #(bold green). The format string in the previous example will print log messages in magenta.

You can also style a message directly:

logger.info('#(underlined green)This will be underlined and green!')

We use shell codes to color the output, so using this formatter with anything but a StreamHandler connected to stdout is not useful or recommended.

We check if stdout is a terminal; if stdout is piped to a file or program, the color codes will not be printed. Support for stderr should be added in the future.

Colors and Styles

The syntax for modifiers is #([style] [color]), where style and color are one of the following:

Styles	Colors
[not] bold	black
[not] underlined	white
[not] dim	[light] gray
[not] blink	[light] red
[not] inverted	[light] green
[not] hidden	[light] yellow
plain	[light] blue
	[light] magenta
	[light] cyan
	level

Colors and styles can be combined; for example bold red, bold light red, etc.

red blue will parse fine, but you'll just get blue output. Unfortunately we can't do color mixing with shell codes.

plain clears all styles and colors.

level is a special color that depends on the log level of the message. By default info is green, warning is yellow, etc. The most common use case would be coloring the level name:

fmt = "%(asctime)s #(level)%(levelname)s#(plain): %(message)s"
formatter = ColorFormatter(fmt)

Note the usage of plain; without it the message would be colored too.

The defaults can be changed, or new levels added, with the setLevelColor method:

formatter.setLevelColor(logging.INFO, 'inverted light cyan')

Options

ColorFormatter's behaviour depends on two options:

additive: in additive mode, colors and styles are applied cumulatively. Otherwise, style modifiers clear all previous modifiers. The default is False. Example:

formatter = ColorFormatter(additive=True)
handler.setFormatter(formatter)

logger.info('#(bold)This is bold. #(blue)This is bold and blue. #(not bold)This is blue.')

formatter = ColorFormatter()  # additive is False by default
handler.setFormatter(formatter)

logger.info('#(bold)This is bold. #(blue)This is only blue, not bold.')

Negative modifiers, e.g. #(not bold) can be used in additive mode for complex styling.

Note that the negative modifiers do not work correctly in some terminal emulators.

autoclear: adds #(plain) at the end of every message. Defaults to True. If set to False and #(plain)is omitted, the shell will continue printing in whatever style was set, past the log line.

Todo

• Make ColorFormatter useable with stderr (only problem is that the TTY check is currently hardcoded to stdout.)
• Add background colors
• Add 88 and 256 color modes
• Re-implement negative modifiers with no-style code since support for style clear codes is really iffy.
• Windows support? (Do people use python command line programs on Windows?)