How can I color Python logging output?

Some time ago, I saw a Mono application with colored output, presumably because of its log system (because all the messages were standardized).

Now, Python has the logging module, which lets you specify a lot of options to customize output. So, I'm imagining something similar would be possible with Python, but I can't find out how to do this anywhere.

Is there any way to make the Python logging module output in color?

What I want (for instance) errors in red, debug messages in blue or yellow, and so on.

Of course this would probably require a compatible terminal (most modern terminals are); but I could fallback to the original logging output if color isn't supported.

Any ideas how I can get colored output with the logging module?


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 = "33[0m"
COLOR_SEQ = "33[1;%dm"
BOLD_SEQ = "33[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.

Be careful if you're using more than one logger or handler: ColoredFormatter is changing the record object, which is passed further to other handlers or propagated to other loggers. If you have configured file loggers etc. you probably don't want to have the colors in the log files. To avoid that, it's probably best to simply create a copy of record with copy.copy() before manipulating the levelname attribute, or to reset the levelname to the previous value, before returning the formatted string (credit to Michael in the comments).


Years ago I wrote a colored stream handler for my own use. Then I came across this page and found a collection of code snippets that people are copy/pasting :-(. My stream handler currently only works on UNIX (Linux, Mac OS X) but the advantage is that it's available on PyPI (and GitHub) and it's dead simple to use. It also has a Vim syntax mode :-). In the future I might extend it to work on Windows.

To install the package:

$ pip install coloredlogs

To confirm that it works:

$ coloredlogs --demo

To get started with your own code:

$ python
> import coloredlogs, logging
> coloredlogs.install()
> logging.info("It works!")
2014-07-30 21:21:26 peter-macbook root[7471] INFO It works!

The default log format shown in the above example contains the date, time, hostname, the name of the logger, the PID, the log level and the log message. This is what it looks like in practice:

coloredlogs输出的屏幕截图


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())
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