How can I make the Python logging output to be colored?

Question

Some time ago I saw a Mono application with colored output, probably because of it's log system, because all the messages were standardized.
Now, Python has the logging module, and it let you specify a lot of options or customize it entirely, so I'm imagining that something like that would be possible too with Python, however I could not find it anywhere. Is there any way to make the Python logging module to output in color? What I want is for error messages to appear in red, for instance. Debug messages in blue or yellow, and so on.
Of course this would probably only work on Linux, with compatible terminals (most modern terminals are), but I could fallback to the original logging output if color is not supported.

Any ideas?

Answer 1

Googling for a quick bash example of colored output I grabbed this line:

"\033[1mChoose one of the following persons:\033[0m"

then a quick vi edit of a tmp file

print "\033[1mChoose one of the following persons:\033[0m"

and ran it... looks like it works but only in a bash shell on *nix.

Very likely an easier way to do it, but probably need to make your own logging.Formatter class to append the right color codes according to your criteria ( red for error, yellow for warning, and green for info/debug ).

Answer 2

I believe (as David has alluded to) that you need to look into escape characters. There seems to be a pretty good tutorial here with an example (in C) but the concept should be the same. But a general google for terminal escape characters should point you in the right direction.

Answer 3

I already knew about the color escapes, I used them in my bash prompt a while ago. Thanks anyway.
What I wanted was to integrate it with the logging module, which I eventually did after a couple of tries and errors.
Here is what I end up with:

BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE = range(8)

#The background is set with 40 plus the number of the color, and the foreground with 30

#These are the sequences need to get colored ouput
RESET_SEQ = "\033[0m"
COLOR_SEQ = "\033[1;%dm"
BOLD_SEQ = "\033[1m"

def formatter_message(message, use_color = True):
    if use_color:
        message = message.replace("$RESET", RESET_SEQ).replace("$BOLD", BOLD_SEQ)
    else:
        message = message.replace("$RESET", "").replace("$BOLD", "")
    return message

COLORS = {
    'WARNING': YELLOW,
    'INFO': WHITE,
    'DEBUG': BLUE,
    'CRITICAL': YELLOW,
    'ERROR': RED
}

class ColoredFormatter(logging.Formatter):
    def __init__(self, msg, use_color = True):
        logging.Formatter.__init__(self, msg)
        self.use_color = use_color

    def format(self, record):
        levelname = record.levelname
        if self.use_color and levelname in COLORS:
            levelname_color = COLOR_SEQ % (30 + COLORS[levelname]) + levelname + RESET_SEQ
            record.levelname = levelname_color
        return logging.Formatter.format(self, record)

And to use it, create your own Logger:

# Custom logger class with multiple destinations
class ColoredLogger(logging.Logger):
    FORMAT = "[$BOLD%(name)-20s$RESET][%(levelname)-18s]  %(message)s ($BOLD%(filename)s$RESET:%(lineno)d)"
    COLOR_FORMAT = formatter_message(FORMAT, True)
    def __init__(self, name):
        logging.Logger.__init__(self, name, logging.DEBUG)                

        color_formatter = ColoredFormatter(self.COLOR_FORMAT)

        console = logging.StreamHandler()
        console.setFormatter(color_formatter)

        self.addHandler(console)
        return


logging.setLoggerClass(ColoredLogger)

Just in case anyone else needs it.

Answer 4

Here is a solution that should work on any platform. If it doesn't just tell me and I will update it.

How it works: on platform supporting ANSI escapes is using them (non-Windows) and on Windows it does use API calls to change the console colors.

The script does hack the logging.StreamHandler.emit method from standard library adding a wrapper to it.

TestColorer.py

# Usage: add Colorer.py near you script and import it.
import logging
import Colorer

logging.warn("a warning")
logging.error("some error")
logging.info("some info")

Colorer.py

#!/usr/bin/env python
# encoding: utf-8
import logging
# now we patch Python code to add color support to logging.StreamHandler
def add_coloring_to_emit_windows(fn):
        # add methods we need to the class
    def _out_handle(self):
        import ctypes
        return ctypes.windll.kernel32.GetStdHandle(self.STD_OUTPUT_HANDLE)
    out_handle = property(_out_handle)

    def _set_color(self, code):
        import ctypes
        # Constants from the Windows API
        self.STD_OUTPUT_HANDLE = -11
        hdl = ctypes.windll.kernel32.GetStdHandle(self.STD_OUTPUT_HANDLE)
        ctypes.windll.kernel32.SetConsoleTextAttribute(hdl, code)

    setattr(logging.StreamHandler, '_set_color', _set_color)

    def new(*args):
        FOREGROUND_BLUE      = 0x0001 # text color contains blue.
        FOREGROUND_GREEN     = 0x0002 # text color contains green.
        FOREGROUND_RED       = 0x0004 # text color contains red.
        FOREGROUND_INTENSITY = 0x0008 # text color is intensified.
        FOREGROUND_WHITE     = FOREGROUND_BLUE|FOREGROUND_GREEN |FOREGROUND_RED
       # winbase.h
        STD_INPUT_HANDLE = -10
        STD_OUTPUT_HANDLE = -11
        STD_ERROR_HANDLE = -12

        # wincon.h
        FOREGROUND_BLACK     = 0x0000
        FOREGROUND_BLUE      = 0x0001
        FOREGROUND_GREEN     = 0x0002
        FOREGROUND_CYAN      = 0x0003
        FOREGROUND_RED       = 0x0004
        FOREGROUND_MAGENTA   = 0x0005
        FOREGROUND_YELLOW    = 0x0006
        FOREGROUND_GREY      = 0x0007
        FOREGROUND_INTENSITY = 0x0008 # foreground color is intensified.

        BACKGROUND_BLACK     = 0x0000
        BACKGROUND_BLUE      = 0x0010
        BACKGROUND_GREEN     = 0x0020
        BACKGROUND_CYAN      = 0x0030
        BACKGROUND_RED       = 0x0040
        BACKGROUND_MAGENTA   = 0x0050
        BACKGROUND_YELLOW    = 0x0060
        BACKGROUND_GREY      = 0x0070
        BACKGROUND_INTENSITY = 0x0080 # background color is intensified.     

        levelno = args[1].levelno
        if(levelno>=50):
            color = BACKGROUND_YELLOW | FOREGROUND_RED | FOREGROUND_INTENSITY | BACKGROUND_INTENSITY 
        elif(levelno>=40):
            color = FOREGROUND_RED | FOREGROUND_INTENSITY
        elif(levelno>=30):
            color = FOREGROUND_YELLOW | FOREGROUND_INTENSITY
        elif(levelno>=20):
            color = FOREGROUND_GREEN
        elif(levelno>=10):
            color = FOREGROUND_MAGENTA
        else:
            color =  FOREGROUND_WHITE
        args[0]._set_color(color)

        ret = fn(*args)
        args[0]._set_color( FOREGROUND_WHITE )
        #print "after"
        return ret
    return new

def add_coloring_to_emit_ansi(fn):
    # add methods we need to the class
    def new(*args):
        levelno = args[1].levelno
        if(levelno>=50):
            color = '\x1b[31m' # red
        elif(levelno>=40):
            color = '\x1b[31m' # red
        elif(levelno>=30):
            color = '\x1b[33m' # yellow
        elif(levelno>=20):
            color = '\x1b[32m' # green 
        elif(levelno>=10):
            color = '\x1b[35m' # pink
        else:
            color = '\x1b[0m' # normal
        args[1].msg = color + args[1].msg +  '\x1b[0m'  # normal
        #print "after"
        return fn(*args)
    return new

import platform
if platform.system()=='Windows':
    # Windows does not support ANSI escapes and we are using API calls to set the console color
    logging.StreamHandler.emit = add_coloring_to_emit_windows(logging.StreamHandler.emit)
else:
    # all non-Windows platforms are supporting ANSI escapes so we use them
    logging.StreamHandler.emit = add_coloring_to_emit_ansi(logging.StreamHandler.emit)
    #log = logging.getLogger()
    #log.addFilter(log_filter())
    #//hdlr = logging.StreamHandler()
    #//hdlr.setFormatter(formatter())

Answer 5

I modified the original example provided by Sorin and subclassed StreamHandler to a ColorizedConsoleHandler.

The downside of their solution is that it modifies the message, and because that is modifying the actual logmessage any other handlers will get the modified message as well.

This resulted in logfiles with colorcodes in them in our case because we use multiple loggers.

The class below only works on platforms that support ansi, but it should be trivial to add the windows colorcodes to it.

import copy, logging
class ColoredConsoleHandler( logging.StreamHandler ):
def emit( self, record ):
    # Need to make a actual copy of the record 
    # to prevent altering the message for other loggers
    myrecord = copy.copy( record )
    levelno = myrecord.levelno
    if( levelno >= 50 ): # CRITICAL / FATAL
        color = '\x1b[31m' # red
    elif( levelno >= 40 ): # ERROR
        color = '\x1b[31m' # red
    elif( levelno >= 30 ): # WARNING
        color = '\x1b[33m' # yellow
    elif( levelno >= 20 ): # INFO
        color = '\x1b[32m' # green
    elif( levelno >= 10 ): # DEBUG
        color = '\x1b[35m' # pink
    else: # NOTSET and anything else
        color = '\x1b[0m' # normal
    myrecord.msg = color + str( myrecord.msg ) + '\x1b[0m'  # normal
    logging.StreamHandler.emit( self, myrecord )

Answer 6

I updated the example from airmind supporting tags for foreground and background. Just use the color variables $BLACK - $WHITE in your log formatter string. To set the background just use $BG-BLACK - $BG-WHITE.

import logging

BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE = range(8)

COLORS = {
    'WARNING'  : YELLOW,
    'INFO'     : WHITE,
    'DEBUG'    : BLUE,
    'CRITICAL' : YELLOW,
    'ERROR'    : RED,
    'RED'      : RED,
    'GREEN'    : GREEN,
    'YELLOW'   : YELLOW,
    'BLUE'     : BLUE,
    'MAGENTA'  : MAGENTA,
    'CYAN'     : CYAN,
    'WHITE'    : WHITE,
}

RESET_SEQ = "\033[0m"
COLOR_SEQ = "\033[1;%dm"
BOLD_SEQ  = "\033[1m"

class ColorFormatter(logging.Formatter):

    def __init__(self, *args, **kwargs):
        # can't do super(...) here because Formatter is an old school class
        logging.Formatter.__init__(self, *args, **kwargs)

    def format(self, record):
        levelname = record.levelname
        color     = COLOR_SEQ % (30 + COLORS[levelname])
        message   = logging.Formatter.format(self, record)
        message   = message.replace("$RESET", RESET_SEQ)\
                           .replace("$BOLD",  BOLD_SEQ)\
                           .replace("$COLOR", color)
        for k,v in COLORS.items():
            message = message.replace("$" + k,    COLOR_SEQ % (v+30))\
                             .replace("$BG" + k,  COLOR_SEQ % (v+40))\
                             .replace("$BG-" + k, COLOR_SEQ % (v+40))
        return message + RESET_SEQ

logging.ColorFormatter = ColorFormatter

So now you can simple do the following in your config file:

[formatter_colorFormatter]
class=logging.ColorFormatter
format= $COLOR%(levelname)s $RESET %(asctime)s $BOLD$COLOR%(name)s$RESET %(message)s

Answer 7

Another minor remix of airmind's approach that keeps everything in one class:

class ColorFormatter(logging.Formatter):
  FORMAT = ("[$BOLD%(name)-20s$RESET][%(levelname)-18s]  "
            "%(message)s "
            "($BOLD%(filename)s$RESET:%(lineno)d)")

  BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE = range(8)

  RESET_SEQ = "\033[0m"
  COLOR_SEQ = "\033[1;%dm"
  BOLD_SEQ = "\033[1m"

  COLORS = {
    'WARNING': YELLOW,
    'INFO': WHITE,
    'DEBUG': BLUE,
    'CRITICAL': YELLOW,
    'ERROR': RED
  }

  def formatter_msg(self, msg, use_color = True):
    if use_color:
      msg = msg.replace("$RESET", self.RESET_SEQ).replace("$BOLD", self.BOLD_SEQ)
    else:
      msg = msg.replace("$RESET", "").replace("$BOLD", "")
    return msg

  def __init__(self, use_color=True):
    msg = self.formatter_msg(self.FORMAT, use_color)
    logging.Formatter.__init__(self, msg)
    self.use_color = use_color

  def format(self, record):
    levelname = record.levelname
    if self.use_color and levelname in self.COLORS:
      fore_color = 30 + self.COLORS[levelname]
      levelname_color = self.COLOR_SEQ % fore_color + levelname + self.RESET_SEQ
      record.levelname = levelname_color
    return logging.Formatter.format(self, record)

To use attach the formatter to a handler, something like:

handler.setFormatter(ColorFormatter())
logger.addHandler(handler)

Answer 8

Here is my solution. I think that by splitting it up into modules you can get cleaner code

http://paste.ofcode.org/33VBitj9AwyGCMzEDqLkdHa