Json Formatter for the standard python logger
Latest commit b36cfa4 Feb 25, 2017 @madzak Version Bump (again)


Build Status


This library is provided to allow standard python logging to output log data as json objects. With JSON we can make our logs more readable by machines and we can stop writing custom parsers for syslog type records.



pip install python-json-logger




python setup.py install


Json outputs are provided by the JsonFormatter logging formatter. You can add the customer formatter like below:

Please note: version 0.1.0 has changed the import structure, please update to the following example for proper importing

    import logging
    from pythonjsonlogger import jsonlogger

    logger = logging.getLogger()

    logHandler = logging.StreamHandler()
    formatter = jsonlogger.JsonFormatter()

The fmt parser can also be overidden if you want to use an alternate from the default.

    class CustomJsonFormatter(jsonlogger.JsonFormatter):
      def parse(self):
          return eval(self._fmt)

You can also add extra fields to your json output by specifying a dict in place of message, as well as by specifying an extra={} argument. Contents of these dictionaries will be added at the root level of the entry and may override basic fields. For custom handling of object serialization you can specify default json object translator or provide a custom encoder

    def json_translate(obj):
        if isinstance(obj, MyClass):
            return {"special": obj.special}

    formatter = jsonlogger.JsonFormatter(json_default=json_translate,

    logger.info({"special": "value", "run": 12})
    logger.info("classic message", extra={"special": "value", "run": 12})

With a Config File

To use the module with a config file using the fileConfig function, use the class pythonjsonlogger.jsonlogger.JsonFormatter. Here is a sample config file.

keys = root,custom

handlers = 

level = INFO
handlers = custom
qualname = custom

keys = custom

class = StreamHandler
level = INFO
formatter = json
args = (sys.stdout,)

keys = json

format = %(message)s
class = pythonjsonlogger.jsonlogger.JsonFormatter


Sample JSON with a full formatter (basically the log message from the unit test). Every log message will appear on 1 line like a typical logger.

    "threadName": "MainThread", 
    "name": "root", 
    "thread": 140735202359648, 
    "created": 1336281068.506248, 
    "process": 41937, 
    "processName": "MainProcess", 
    "relativeCreated": 9.100914001464844, 
    "module": "tests", 
    "funcName": "testFormatKeys", 
    "levelno": 20, 
    "msecs": 506.24799728393555, 
    "pathname": "tests/tests.py", 
    "lineno": 60, 
    "asctime": ["12-05-05 22:11:08,506248"], 
    "message": "testing logging format", 
    "filename": "tests.py", 
    "levelname": "INFO",
    "special": "value",
    "run": 12