Colored log output for Python logging framework. Works on Windows, Linux, and probably Mac as well.

colorstreamhandler.py

# colored stream handler for python logging framework (use the ColorStreamHandler class).
#
# based on:
# http://stackoverflow.com/questions/384076/how-can-i-color-python-logging-output/1336640#1336640

# how to use:
# i used a dict-based logging configuration, not sure what else would work.
#
# import logging, logging.config, colorstreamhandler
# 
# _LOGCONFIG = {
#     "version": 1,
#     "disable_existing_loggers": False,
# 
#     "handlers": {
#         "console": {
#             "class": "colorstreamhandler.ColorStreamHandler",
#             "stream": "ext://sys.stderr",
#             "level": "INFO"
#         }
#     },
# 
#     "root": {
#         "level": "INFO",
#         "handlers": ["console"]
#     }
# }
# 
# logging.config.dictConfig(_LOGCONFIG)
# mylogger = logging.getLogger("mylogger")
# mylogger.warning("foobar")
 
# Copyright (c) 2014 Markus Pointner
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

import logging

class _AnsiColorStreamHandler(logging.StreamHandler):
    DEFAULT = '\x1b[0m'
    RED     = '\x1b[31m'
    GREEN   = '\x1b[32m'
    YELLOW  = '\x1b[33m'
    CYAN    = '\x1b[36m'

    CRITICAL = RED
    ERROR    = RED
    WARNING  = YELLOW
    INFO     = GREEN
    DEBUG    = CYAN

    @classmethod
    def _get_color(cls, level):
        if level >= logging.CRITICAL:  return cls.CRITICAL
        elif level >= logging.ERROR:   return cls.ERROR
        elif level >= logging.WARNING: return cls.WARNING
        elif level >= logging.INFO:    return cls.INFO
        elif level >= logging.DEBUG:   return cls.DEBUG
        else:                          return cls.DEFAULT

    def __init__(self, stream=None):
        logging.StreamHandler.__init__(self, stream)

    def format(self, record):
        text = logging.StreamHandler.format(self, record)
        color = self._get_color(record.levelno)
        return color + text + self.DEFAULT

class _WinColorStreamHandler(logging.StreamHandler):
    # 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.
    FOREGROUND_WHITE     = FOREGROUND_BLUE | FOREGROUND_GREEN | FOREGROUND_RED

    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.

    DEFAULT  = FOREGROUND_WHITE
    CRITICAL = BACKGROUND_YELLOW | FOREGROUND_RED | FOREGROUND_INTENSITY | BACKGROUND_INTENSITY
    ERROR    = FOREGROUND_RED | FOREGROUND_INTENSITY
    WARNING  = FOREGROUND_YELLOW | FOREGROUND_INTENSITY
    INFO     = FOREGROUND_GREEN
    DEBUG    = FOREGROUND_CYAN

    @classmethod
    def _get_color(cls, level):
        if level >= logging.CRITICAL:  return cls.CRITICAL
        elif level >= logging.ERROR:   return cls.ERROR
        elif level >= logging.WARNING: return cls.WARNING
        elif level >= logging.INFO:    return cls.INFO
        elif level >= logging.DEBUG:   return cls.DEBUG
        else:                          return cls.DEFAULT

    def _set_color(self, code):
        import ctypes
        ctypes.windll.kernel32.SetConsoleTextAttribute(self._outhdl, code)

    def __init__(self, stream=None):
        logging.StreamHandler.__init__(self, stream)
        # get file handle for the stream
        import ctypes, ctypes.util
        # for some reason find_msvcrt() sometimes doesn't find msvcrt.dll on my system?
        crtname = ctypes.util.find_msvcrt()
        if not crtname:
            crtname = ctypes.util.find_library("msvcrt")
        crtlib = ctypes.cdll.LoadLibrary(crtname)
        self._outhdl = crtlib._get_osfhandle(self.stream.fileno())

    def emit(self, record):
        color = self._get_color(record.levelno)
        self._set_color(color)
        logging.StreamHandler.emit(self, record)
        self._set_color(self.FOREGROUND_WHITE)

# select ColorStreamHandler based on platform
import platform
if platform.system() == 'Windows':
    ColorStreamHandler = _WinColorStreamHandler
else:
    ColorStreamHandler = _AnsiColorStreamHandler

How can I use it?

@twmht

something like (not tested)

import logging
import logging.handlers

my_logger = logging.getLogger('MyLogger')
my_logger.setLevel(logging.DEBUG)

my_logger.addHandler(ColorStreamHandler)  ## <- Just added it

my_logger.debug('this is debug')
my_logger.critical('this is critical')

This failed for me on Windows with Python 3.5 x86_64.

Exchanged line 104 for this:

        crtname = ctypes.util.find_msvcrt()
        if not crtname:
            crtname = ctypes.util.find_library("msvcrt")

There's a small typo on the Windows version. Change line 106 to:

self._outhdl = crtlib._get_osfhandle(self.stream.fileno())

Edit: Thanks, this is now fixed in the latest version.

in linux color escapes are redirected to file too. Here's a fix:

1. add new property:

@property
def is_tty(self):
    isatty = getattr(self.stream, 'isatty', None)
    return isatty and isatty()

2. modify 'format' method:

    if self.is_tty:
        return color + text + self.DEFAULT
    else:
        return text

thanks to plumberjack

The following line fails from jupyter notebook or ipython in windows:

Line 106: self._outhdl = crtlib._get_osfhandle(self.stream.fileno())

In this case IOStream object has no fileno method

C:\Program Files (x86)\Anaconda2\envs\py36\lib\logging\config.py in configure(self)
    557                     try:
--> 558                         handler = self.configure_handler(handlers[name])
    559                         handler.name = name

C:\Program Files (x86)\Anaconda2\envs\py36\lib\logging\config.py in configure_handler(self, config)
    730         try:
--> 731             result = factory(**kwargs)
    732         except TypeError as te:

~\AppData\Local\myproj\misc\colorstreamhandler.py in __init__(self, stream)
    158         crtlib = ctypes.cdll.LoadLibrary(crtname)
--> 159         self._outhdl = crtlib._get_osfhandle(self.stream.fileno())
    160 

UnsupportedOperation: fileno