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Robust and effective logging for Python 2 and 3

Project description


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Robust and effective logging for Python 2 and 3.



  • Easy logging to console and/or (rotating) file.
  • Provides a fully configured standard Python logger object.
  • JSON logging (with integrated python-json-logger)
  • Pretty formatting, including level-specific colors in the console.
  • No dependencies
  • Windows color output supported by colorama
  • Robust against str/bytes encoding problems, works with all kinds of character encodings and special characters.
  • Multiple loggers can write to the same logfile (also across multiple Python files and processes).
  • Global default logger with logzero.logger and custom loggers with logzero.setup_logger(..).
  • Compatible with Python 2 and 3.
  • All contained in a single file.
  • Licensed under the MIT license.
  • Heavily inspired by the Tornado web framework.


python -m pip install logzero

Example Usage

from logzero import logger


# This is how you'd log an exception
    raise Exception("this is a demo exception")
except Exception as e:

# JSON logging
import logzero
logzero.json()"JSON test")

# Start writing into a logfile

# Set a minimum loglevel

This is the output:


Note: You can find more examples in the documentation:

JSON logging

JSON logging can be enabled for the default logger with logzero.json(), or with setup_logger(json=True) for custom loggers:

>>> logzero.json()
{"asctime": "2020-10-21 10:42:45,808", "filename": "<stdin>", "funcName": "<module>", "levelname": "INFO", "levelno": 20, "lineno": 1, "module": "<stdin>", "message": "test", "name": "logzero_default", "pathname": "<stdin>", "process": 76179, "processName": "MainProcess", "threadName": "MainThread"}

>>> my_logger = setup_logger(json=True)
{"asctime": "2020-10-21 10:42:45,808", "filename": "<stdin>", "funcName": "<module>", "levelname": "INFO", "levelno": 20, "lineno": 1, "module": "<stdin>", "message": "test", "name": "logzero_default", "pathname": "<stdin>", "process": 76179, "processName": "MainProcess", "threadName": "MainThread"}

The logged JSON object has these fields:

  "asctime": "2020-10-21 10:43:40,765",
  "filename": "",
  "funcName": "test_this",
  "levelname": "INFO",
  "levelno": 20,
  "lineno": 9,
  "module": "test",
  "message": "info",
  "name": "logzero",
  "pathname": "_tests/",
  "process": 76204,
  "processName": "MainProcess",
  "threadName": "MainThread"

Exceptions logged with logger.exception(e) have these additional JSON fields:

  "levelname": "ERROR",
  "levelno": 40,
  "message": "this is a demo exception",
  "exc_info": "Traceback (most recent call last):\n  File \"_tests/\", line 15, in test_this\n    raise Exception(\"this is a demo exception\")\nException: this is a demo exception"

Take a look at the documentation for more information and examples:


Install logzero with pip:

python -m pip install logzero

Here's how you setup a virtualenv and download and run the demo:

# Create and activate a virtualenv in ./venv/
python3 -m venv venv
. venv/bin/activate

# Install logzero
python -m pip install logzero

# Download and run

If you don't have pip installed, this Python installation guide can guide you through the process.

Alternatively, if you use the Anaconda distribution:

$ conda config --add channels conda-forge
$ conda install logzero

You can also install logzero from the public Github repo:

$ git clone
$ cd logzero
$ python install



Getting started

$ git clone
$ cd logzero

# Activate virtualenv
$ python3 -m venv venv
$ . venv/bin/activate

# Install main and dev dependencies
$ pip install -e .
$ pip install -r requirements_dev.txt

# Run the tests
$ make test

# Run the linter
$ make lint

# Generate the docs (will auto-open in Chrome)
$ make docs

# You can enable watching mode to automatically rebuild on changes:
$ make servedocs

To test with Python 2.7, you can use Docker:

docker run --rm -it -v /Users/chris/stream/logzero:/mnt python:2.7 /bin/bash

Now you have a shell with the current directory mounted into /mnt/ inside the container.



See the changelog here:


All kinds of feedback and contributions are welcome.



1.6.5 (2021-03-17)

  • Export loglevels directly (you can use eg. logzero.DEBUG instead of logging.DEBUG)
  • setup_default_logger use backupCount
  • Update dependencies
  • PRs: (386)[]

1.6.3 (2020-11-15)

  • JSON logging with UTF-8 enabled by default (PR 357)

1.6.0 (1.6.2) (2020-10-29)

  • JSON logging support (PR 344)
  • Ability to easily change colors (#82)
  • Allow creating a root logger (#342)
  • Bugfix: file logging with lower loglevel than stream (PR 338)
  • Running tests with Python up to 3.9
  • Dependency updates

1.5.0 (2018-03-07)

  • logzero.syslog(..) (PR 83)

1.4.0 (2018-03-02)

  • Allow Disabling stderr Output (PR 83)

1.3.0 (2017-07-19)

  • Color output now works in Windows (supported by colorama)

1.2.1 (2017-07-09)

  • Logfiles with custom loglevels (eg. stream handler with DEBUG and file handler with ERROR).

1.2.0 (2017-07-05)

  • Way better API for configuring the default logger with logzero.loglevel(..), logzero.logfile(..), etc.
  • Built-in rotating logfile support.
import logging
import logzero
from logzero import logger

# This log message goes to the console

# Set a minimum log level

# Set a logfile (all future log messages are also saved there)

# Set a rotating logfile (replaces the previous logfile handler)
logzero.logfile("/tmp/rotating-logfile.log", maxBytes=1000000, backupCount=3)

# Disable logging to a file

# Set a custom formatter
formatter = logging.Formatter('%(name)s - %(asctime)-15s - %(levelname)s: %(message)s');

# Log some variables"var1: %s, var2: %s", var1, var2)

1.1.2 (2017-07-04)

  • Better reconfiguration of handlers, doesn't remove custom handlers anymore

1.1.0 (2017-07-03)

  • Bugfix: Disabled color logging to logfile

1.1.0 (2017-07-02)

  • Global default logger instance (logzero.logger)
  • Ability to reconfigure the default logger with (logzero.setup_default_logger(..))
  • More tests
  • More documentation

1.0.0 (2017-06-27)

  • Cleanup and documentation

0.2.0 (2017-06-12)

  • Working logzero package with code and tests

0.1.0 (2017-06-12)

  • First release on PyPI.

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