Optimal solution for coloring logging output

[Jean-Michel Pichavant]

---- Original Message -----
> From: "c buhtz" <c.buhtz at posteo.jp>
> To: python-list at python.org
> Sent: Monday, 3 August, 2015 11:13:37 AM
> Subject: Optimal solution for coloring logging output
> 
> I don't want to ask how to do this because there are so many
> "solutions" about it.
> <http://stackoverflow.com/questions/384076/how-can-i-color-python-logging-output>
> 
> There are so much different and part of unpythontic solutions I can
> not
> decide myself. What do you (as real pythontics) think about that.
> Which of the solutions fit to concepts of Python and its logging
> package?
> 
> Coloring means here not only the message itself. The (levelname)
> should
> be included in the coloring.
> For myself coloring the (levelname) would be enough to avoid to much
> color in the output.
> 
> 1.
> The solution itself shouldn't care about plattform differences
> because
> there are still some packages which are able to offer
> plattform-independent console-coloring. Which would you prefere? ;)
> 
> 2.
> Some solutions derive from StreamHandler or much more bad hacking the
> emit() function. I think both of them are not responsible for how the
> output should look or be presented.
> 
> 3.
> How to present the output is IMO the responsibility of a Formater,
> isn't
> it? So I should derive from the Formater.
> 
> What do you as Pythonics think of that? ;)

This is more or less how it could be done:

1/ use the module "curses" to get terminal colors (the doc suggests to use the "Console" moduel on windows)
2/ write a logging Formatter that will replace DEBUG/INFO/ERROR message by their colored version.


import curses
import logging
import string
import re

curses.setupterm()
class ColorFormat:
	#{ Foregroung colors
	BLACK = curses.tparm(curses.tigetstr('setaf'), curses.COLOR_BLACK)
	RED = curses.tparm(curses.tigetstr('setaf'), curses.COLOR_RED)
	GREEN = curses.tparm(curses.tigetstr('setaf'), curses.COLOR_GREEN)
	YELLOW = curses.tparm(curses.tigetstr('setaf'), curses.COLOR_YELLOW)
	BLUE = curses.tparm(curses.tigetstr('setaf'), curses.COLOR_BLUE)
	MAGENTA = curses.tparm(curses.tigetstr('setaf'), curses.COLOR_MAGENTA)
	CYAN = curses.tparm(curses.tigetstr('setaf'), curses.COLOR_CYAN)
	WHITE = curses.tparm(curses.tigetstr('setaf'), 9) # default white is 7, the 9 is a better white
	#{ Backgrounds colors
	BG_BLACK = curses.tparm(curses.tigetstr('setab'), curses.COLOR_BLACK)
	BG_RED = curses.tparm(curses.tigetstr('setab'), curses.COLOR_RED)
	BG_GREEN = curses.tparm(curses.tigetstr('setab'), curses.COLOR_GREEN)
	BG_YELLOW = curses.tparm(curses.tigetstr('setab'), curses.COLOR_YELLOW)
	BG_BLUE = curses.tparm(curses.tigetstr('setab'), curses.COLOR_BLUE)
	BG_MAGENTA = curses.tparm(curses.tigetstr('setab'), curses.COLOR_MAGENTA)
	BG_CYAN = curses.tparm(curses.tigetstr('setab'), curses.COLOR_CYAN)
	BG_WHITE = curses.tparm(curses.tigetstr('setab'), curses.COLOR_WHITE) 
	#{ Format codes
	BOLD = curses.tparm(curses.tigetstr('bold'), curses.A_BOLD)
	UNDERLINE = curses.tparm(curses.tigetstr('smul'), curses.A_UNDERLINE)
	BLINK = curses.tparm(curses.tigetstr('blink'), curses.A_BLINK)
	NO_FORMAT = curses.tparm(curses.tigetstr('sgr0'), curses.A_NORMAL)
	NO_COLOR = curses.tigetstr('sgr0')
	#}

def setFormat(attributeList):
	_set = '' # avoid collision with the builtin set type
	for attribute in attributeList:
		_set += getattr(ColorFormat, attribute, '')
	return _set

class ColorFormatter(logging.Formatter):
	def format(self, record):
		parameters = record.__dict__.copy()
		parameters['message'] = record.getMessage()
				
		# ------------------------------------------------------------------
		# Log Level Format : %(levelname)
		# ------------------------------------------------------------------
		fmt = self._fmt
		pattern = r'(%\(levelname\)(?:-?\d+)?s)'
		if record.levelno <= logging.DEBUG:
			fmt = re.sub(pattern, setFormat(['BLUE']) + r'\1' + 
						 setFormat(['NO_COLOR']), fmt)
		elif record.levelno <= logging.INFO:
			fmt = re.sub(pattern, setFormat(['CYAN']) + r'\1' + 
						 setFormat(['NO_COLOR']), fmt)
		elif record.levelno <= logging.WARNING:
			fmt = re.sub(pattern, setFormat(['MAGENTA']) + r'\1' + 
						 setFormat(['NO_COLOR']), fmt)
		elif record.levelno <= logging.ERROR:
			fmt = re.sub(pattern, setFormat(['RED','BOLD']) + r'\1' + 
						 setFormat(['NO_COLOR']), fmt)
		else:
			fmt = re.sub(pattern, setFormat(['WHITE', 'BOLD', 'BG_RED']) + 
						 r'\1' + setFormat(['NO_COLOR']), fmt)
		
		# ------------------------------------------------------------------
		# following is the classic format method from the default formatter
		# ------------------------------------------------------------------
		if string.find(fmt,"%(asctime)") >= 0:
			record.asctime = self.formatTime(record, self.datefmt)
			parameters['asctime'] = record.asctime
		s = fmt % parameters
		if record.exc_info:
			# Cache the traceback text to avoid converting it multiple times
			# (it's constant anyway)
			if not record.exc_text:
				record.exc_text = self.formatException(record.exc_info)
		if record.exc_text:
			if s[-1] != "\n":
				s = s + "\n"
			s = s + record.exc_text
		return s
	
if __name__ == '__main__':
	logger = logging.getLogger('Foo')
	logger.setLevel(logging.DEBUG)
	logger.addHandler(logging.StreamHandler())
	logger.handlers[-1].setFormatter(ColorFormatter('%(levelname)s - %(message)s'))
	logger.error('This is an error')
	logger.debug('This is an debug')


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