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YACL (Yet Another Color Logger) is a simple to use color logger for Python programs.

Project description

YACL - Yet Another Color Logger

Overview

YACL is a very simple to use color logger for Python intended to be used for stderr logging. It can be set up with a single function call in existing projects and enables colored logging output with reasonable defaults. Colors are disabled automatically if stderr is not connected to a tty (e.g. on file redirection) or if not supported by the connected terminal. Currently, Linux and macOS are supported.

You can use Markdown style formattings to produce bold and italic text. Additionally, text enclosed in double underscores will be displayed underlined. YACL checks the terminal capabilities and automatically disables unsupported formats.

Installation

YACL is available on PyPI for Python 3.3+ and can be installed with pip:

python3 -m pip install yacl

Usage

Simple

Call setup_colored_stderr_logging after the root logger has been set up, for example:

#!/usr/bin/env python3

import logging
from yacl import setup_colored_stderr_logging


def main():
    logging.basicConfig(level=logging.DEBUG)
    setup_colored_stderr_logging()


if __name__ == "__main__":
    main()

Afterwards, get module level loggers and use them without any further configuration:

import logging


logger = logging.getLogger(__name__)


def my_func():
    logger.debug('Failed to open file "abc"')

You will get an output like:

screenshot_simple

This example only works if you don't attach any output handlers to loggers other than the root logger as recommended in the Python logging documentation:

If you attach a handler to a logger and one or more of its ancestors, it may emit the same record multiple times. In general, you should not need to attach a handler to more than one logger - if you just attach it to the appropriate logger which is highest in the logger hierarchy, then it will see all events logged by all descendant loggers, provided that their propagate setting is left set to True. A common scenario is to attach handlers only to the root logger, and to let propagation take care of the rest.

Customization

You can pass several arguments to the setup_colored_stderr_logging function to customize the logging behavior:

  • logger: The logger which will be configured to print colored logging output to stderr. By default, the root logger is used.

  • format_string: The format string to use for logging messages. By default the logging format [%(levelname)s] (%(name)s:%(lineno)s:%(funcName)s): %(message)s is used.

    Important: All formats must be passed as string types. For example, in the default format, lineno is given as string ((%lineno)s) and not as number ((%lineno)d).

  • remove_other_handlers: Bool flag to remove all other output handlers on the given logger. Is set to true by default to avoid duplicate logging messages.

  • attribute_colors: A dictionary which assigns colors to logging attributes (which are used in the logging format string). This dictionary is merged with the internal defaults:

    from yacl import TerminalColorCodes
    
    _attribute_colors = {
        "funcName": TerminalColorCodes.blue,
        "lineno": TerminalColorCodes.yellow,
        "name": TerminalColorCodes.cyan,
    }
    
  • keyword_colors: A dictionary which assigns colors to a given regular expressions. This setting can be used to highlight expressions in the logging messages. This dictionary is merged with the internal defaults:

    from yacl import TerminalColorCodes
    
    keyword_colors = {
        r"\bcritical( error)?\b": TerminalColorCodes.red + TerminalColorCodes.blink + TerminalColorCodes.bold,
        r"\bdebug(ged|ging)?\b": TerminalColorCodes.green + TerminalColorCodes.bold,
        r"\berror\b": TerminalColorCodes.red + TerminalColorCodes.bold,
        r"\bfail(ed|ing)?\b": TerminalColorCodes.red + TerminalColorCodes.bold,
        r"\binfo\b": TerminalColorCodes.blue + TerminalColorCodes.bold,
        r"\bwarn(ed|ing)?\b": TerminalColorCodes.yellow + TerminalColorCodes.bold,
        r'"[^"]*"': TerminalColorCodes.yellow,
        r"\*([^*]+)\*": TerminalColorCodes.italics,
        r"\*\*([^*]+)\*\*": TerminalColorCodes.bold,
        r"__([^_]+)__": TerminalColorCodes.underline,
        r"`([^`]+)`": TerminalColorCodes.standout,
    }
    

    Example: Pass a dictionary

    {
        r"'[^']*'": TerminalColorCodes.green + TerminalColorCodes.italics,
    }
    

    to highlight strings in single quotes with green color and italic font (if supported by the Terminal).

  • level_colors: A dictionary which assigns colors to logging levels (DEBUG, INFO, ...). This dictionary is merged with the internal defaults:

    from yacl import TerminalColorCodes
    
    level_colors = {
        "DEBUG": TerminalColorCodes.green + TerminalColorCodes.bold,
        "INFO": TerminalColorCodes.blue + TerminalColorCodes.bold,
        "WARNING": TerminalColorCodes.yellow + TerminalColorCodes.bold,
        "ERROR": TerminalColorCodes.red + TerminalColorCodes.bold,
        "CRITICAL": TerminalColorCodes.red + TerminalColorCodes.blink + TerminalColorCodes.bold,
    }
    

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