Add support for colorized logging output

[derks]

In apps that heavily rely on logging to the console, having colorized output is very useful. For example:

• INFO => No Color
• WARN => Orange
• ERROR => Red
• Critical => Magenta or maybe just Bold Red

[derks]

This might be helpful:

https://gist.github.com/natedub/1101888

[derks]

Also helpful: http://pueblo.sourceforge.net/doc/manual/ansi_color_codes.html

[derks]

An example (slightly hackish) alternative logger with color:

import logging
from colorlog import ColoredFormatter
from cement.core import handler
from cement.utils.misc import is_true
from cement.ext.ext_logging import LoggingLogHandler, NullHandler
from cement.core.controller import expose, CementBaseController

class ColorLogController(CementBaseController):
    class Meta:
        label = 'color_log'
        arguments = [
            (['--no-color'],
             dict(help="disable colorized output", action='store_true')),
        ]

class ColorLogHandler(LoggingLogHandler):
    class Meta:
        label = "color_log"

        #: The logging format for the consoler logger.
        console_format = "%(log_color)s%(levelname)s: %(message)s"

        #: The logging format for both file and console if ``debug==True``.
        debug_format = "%(log_color)s%(asctime)s (%(levelname)s) %(namespace)s : " + \
                       "%(message)s"

    def _setup_console_log(self):
        # Otherwise
        to_console = self.app.config.get(self._meta.config_section,
                                         'to_console')
        if is_true(to_console):
            console_handler = logging.StreamHandler()
            if self.get_level() == logging.getLevelName(logging.DEBUG):
                the_format = self._meta.debug_format
            else:
                the_format = self._meta.console_format

            formatter = ColoredFormatter(the_format,
                            log_colors={
                                'DEBUG':    'white',
                                'INFO':     'green',
                                'WARNING':  'yellow',
                                'ERROR':    'red',
                                'CRITICAL': 'red',
                                })
            console_handler.setFormatter(formatter)
            console_handler.setLevel(getattr(logging, self.get_level()))
        else:
            console_handler = NullHandler()

        self.backend.addHandler(console_handler)

def load():
    handler.register(ColorLogHandler)
    handler.register(ColorLogController)

[spinus]

1. What is the point of turning colors on colorlog, it's not simpler to use standard logger instead?
2. You can detect that output stream is console/tty or not. If not you can use non-color logging (some applications do that, like ls, grep, this feature gives you ability to pipe/chain applications)

[derks]

@spinus are you suggested in 1 to just add the color functionality to LoggingLogHandler rather than sub-classing and having a separate handler?

And in 2 I think that is a good idea to disable coloring if we don't have a tty, that makes sense.

Thanks.

[spinus]

1. No at all. I think there can be two handlers, one standard and one fancy.
   Btw, during the development maybe you would like to watch on this: https://pypi.python.org/pypi/rainbow_logging_handler/2.2.2

[derks]

Yeah, that Rainbow Logging Handler looks pretty much perfect, and seems to have been around for a while. I'll look at doing both (the above doesn't require additional dependencies so it can go in core).

[derks]

This was committed to cement/master based on colorlog:

from cement.core.foundation import CementApp

class MyApp(CementApp):
    class Meta:
        label = 'myapp'
        extensions = ['colorlog']
        log_handler = 'colorlog'

with MyApp() as app:
    app.run()
    app.log.info('My Info Test')
    app.log.error('My Error Test')
    app.log.fatal('My Fatal Test')
    app.log.warn('My Warn Test')
    app.log.debug('My Debug Test')