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Structured JSON logging

Project description


  • Tag log statements with arbitrary values for easier grouping and analysis
  • Add keyword arguments that are converted to JSON values
  • Variable substitution
  • Specifies where log calls are made from
  • Meant to be used with core Python logging (formatters, handlers, etc)
  • Colorized logs on a console (POSIX only)
  • TRACE log level built-in


A simple log message'Hello')

{"msg": "Hello", "time": "12-12-14 10:12:01 EST", "level": "INFO", "loc": "test:log_test:20"}

Logging with tags

log.debug('Creating new user', 'MONGO', 'STORAGE')

{"msg": "Creating new user", "time": "12-12-14 10:12:09 EST", "tags": ["MONGO", "STORAGE"], "level": "DEBUG", "loc": "test:log_test:20"}

Appending more data

log.debug('Some key', is_admin=True, username='papito')

{"msg": "Some key", "is_admin": true, "username": "papito", "time": "12-12-14 10:12:04 EST", "level": "DEBUG", "loc": "test:log_test:20"}

String substitution

log.debug('User "$username" admin? $is_admin', is_admin=False, username='fez')

{"msg": "User \"fez\" admin? False",  "username": "fez", "is_admin": false, "time": "12-12-14 10:12:18 EST", "level": "DEBUG", "loc": "test:log_test:20"}


Logging to console

import sys
import logging
from siftlog import SiftLog

logger = logging.getLogger()
handler = logging.StreamHandler(sys.stdout)

log = SiftLog(logger)

In this fashion, you can direct the JSON logs to any logging handler


For enhanced flamboyancy, attach the ColorStreamHandler to your logger. The output will not have color if the logs are being output to a file, or on systems that are not POSIX (will not work on Windows for now).

from siftlog import SiftLog, ColorStreamHandler

logger = logging.getLogger()
handler = ColorStreamHandler(sys.stdout)

log = SiftLog(logger)

Different colors

You can change font background, text color, and boldness:

from siftlog import ColorStreamHandler

handler = ColorStreamHandler(sys.stdout)
    logging.DEBUG, bg=handler.WHITE, fg=handler.BLUE, bold=True

Supported colors

  • ColorStreamHandler.BLACK
  • ColorStreamHandler.RED
  • ColorStreamHandler.GREEN
  • ColorStreamHandler.YELLOW
  • ColorStreamHandler.BLUE
  • ColorStreamHandler.MAGENTA
  • ColorStreamHandler.CYAN
  • ColorStreamHandler.WHITE

Constants (re-occuring values)

You can define constants that will appear in every single log message. This is useful, for example, if you’d like to log process PID and hostname with every log message (recommended). This is done upon log adapter initialization:

import os
from siftlog import SiftLog
log = SiftLog(logger, pid=os.getpid(), env='INTEGRATION')

{"msg": "And here I am", "time": "12-12-14 11:12:24 EST", "pid": 37463, "env": "INTEGRATION", "level": "INFO"}

Custom time format

log = SiftLog(logger)
SiftLog.TIME_FORMAT = '%d-%m-%y %H:%m:%S %Z'

Define the format as accepted by time.strftime()

Custom location format

log = SiftLog(logger)
SiftLog.LOCATION_FORMAT = '$module:$method:$line_no'

The format should be a string containing any of the following variables:

  • $file
  • $line_no
  • $method
  • $module

Custom core key names

Core keys, such as msg and level can be overridden, if they clash with common keys you might be using.

The following can be redefined:

  • SiftLog.MESSAGE (default msg)
  • SiftLog.LEVEL (default level)
  • SiftLog.LOCATION (default loc)
  • SiftLog.TAGS (default tags)
  • SiftLog.TIME (default time)

As in:

log = SiftLog(logger)

Project details

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