colorlog

6.10.1 · active · verified Sat Mar 28

colorlog is a Python library that adds colors to the output of Python's standard logging module. It currently stands at version 6.10.1 and is in active maintenance, focusing on bug fixes and Python 3 compatibility, rather than major feature additions that might introduce breaking changes.

Warnings

breaking colorlog v6.x dropped support for Python 2 and Python versions older than 3.6. Users needing compatibility with older Python versions (e.g., Python 2.x or 3.5) must pin their dependency to `colorlog<5` or `colorlog<6` respectively.
Fix: Upgrade Python to 3.6+ or pin `colorlog<5` for Python 2.x or `colorlog<6` for Python 3.5.
breaking The internal `TTYColoredFormatter` class was merged into `ColoredFormatter` in version 6.0.0-alpha.2. Direct references to `TTYColoredFormatter` will no longer work.
Fix: Replace `TTYColoredFormatter` with `ColoredFormatter`.
gotcha Logging output redirected to a file or a non-terminal environment will include raw ANSI escape codes, making the file unreadable unless processed by an ANSI-aware viewer. colorlog attempts to detect terminal capabilities but might fail in some setups.
Fix: Ensure `ColoredFormatter` is only used with handlers outputting to terminals (e.g., `logging.StreamHandler`). For file logging, use a standard `logging.Formatter` or configure distinct handlers for terminal vs. file output. You can also use the `no_color` argument or the `NO_COLOR` environment variable to disable colors.
gotcha The `FORCE_COLOR` environment variable can override color detection, forcing colors even if `colorlog` thinks it's not a TTY. Conversely, the `NO_COLOR` environment variable (following the no-color.org standard) can disable colors.
Fix: Be aware of these environment variables when troubleshooting unexpected color behavior in different environments.
deprecated The internal module `colorlog.colorlog` was renamed to `colorlog.formatter`. While direct import from `colorlog.colorlog` might still work for some time due to internal mechanisms, it is considered an internal detail and should not be relied upon.
Fix: Always import `ColoredFormatter` directly from the top-level `colorlog` package (e.g., `from colorlog import ColoredFormatter`).

Install

pip install colorlog Install latest version

Imports

basicConfig

import colorlog
colorlog.basicConfig(...)

ColoredFormatter
```
from colorlog import ColoredFormatter
```
In versions 6.3.0a1 and later, the internal 'colorlog' module was renamed to 'formatter'. Direct import from 'colorlog.colorlog' is deprecated.

Quickstart

This example demonstrates how to set up a basic logger with `colorlog.ColoredFormatter` to get colorized output. It defines custom colors for different logging levels and then logs messages at various severities. Alternatively, for a simpler setup, `colorlog.basicConfig()` can be used, which internally sets up a `ColoredFormatter` for the root logger.

import logging
import colorlog

# Configure a ColoredFormatter
formatter = colorlog.ColoredFormatter(
    '%(log_color)s%(levelname)-8s%(reset)s %(blue)s%(message)s',
    datefmt=None,
    reset=True,
    log_colors={
        'DEBUG':    'cyan',
        'INFO':     'green',
        'WARNING':  'yellow',
        'ERROR':    'red',
        'CRITICAL': 'red,bg_white'
    },
    secondary_log_colors={},
    style='%'
)

# Get the root logger and set its level
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)

# Add a StreamHandler with the colored formatter
handler = logging.StreamHandler()
handler.setFormatter(formatter)
logger.addHandler(handler)

# Example log messages
logger.debug('This is a debug message')
logger.info('This is an info message')
logger.warning('This is a warning message')
logger.error('This is an error message')
logger.critical('This is a critical message')

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