README.md

Easy Custom Logger

The default setup for the logging utility is a little unwieldy to set up for every project - though once done, it is likely to seldom change.

This snippet provides a pre-configured global logging utility allowing for a log level to be set via environment variable, as well as a pretty-print dump() log function that writes when level is set to DEBUG.

By default, logging goes to stdout, but can be redirected to a file.

logger.py

""" Convenience package to get a pre-configured logging object.

In your code, import this package then simply use the logging functions:

    logger.debug(message)
    logger.info(message)
    logger.warning(message)
    logger.error(message)

There is also a debug-level function for dumping data

    logger.dump(data)

The default log level is INFO

This can be adjusted by providing an environment variable
    CUSTOM_LOG_LEVEL

or in-code by calling logger.setLevel()

!! Logging To A File:

Upon importing fcilog , immediately use logger.setLogFile(filename)
This can only be done once, subsequent attempts will raise a
  logger.LoggerConfigException

+++

Copyright: (C) Tai Kedzierski

License: MIT License (see https://mit-license.org/)

You are free to include, adapt and distribute your changes,
 provided you retain this copyright notice.

"""

import os
import logging
import pprint

DEBUG = logging.DEBUG
INFO = logging.INFO
WARNING = logging.WARNING
ERROR = logging.ERROR

__custom_logger = None
__custom_logger_handler = None
__pretty = pprint.PrettyPrinter(indent=2)

__log_file_name = None

def setLogFile(filename):
    # TODO
    # Using logging.basicConfig() in its base form, only
    #   one attempt at setting the file will have sane effects.
    # This code prvents multiple calls to reconfigure file,
    #   but ideally should just switch file

    global __log_file_name

    if __custom_logger is None:
        __log_file_name = filename
        __createLogger(filename)
        return

    if __log_file_name:
        raise LoggerConfigException("Logging is already being written to '{fname}'.".format(fname=__log_file_name) )
    else:
        raise LoggerConfigException("Logging has already started and can no longer be directed to a file.")

def setLevel(level):
    """ Activate a new logging level
    """
    _ = __getLogger()

    __custom_logger.setLevel(level)
    __custom_logger_handler.setLevel(level)

def dump(data):
    logger = __getLogger()
    logger.debug(__pretty.pformat(data))

def debug(message):
    __getLogger().debug(message)

def info(message):
    __getLogger().info(message)

def warning(message):
    __getLogger().warning(message)

def error(message):
    __getLogger().error(message)

def __getLogger():
    if __custom_logger == None:
        __createLogger()

    return __custom_logger

def __createLogger(filename=None):
    global __custom_logger
    global __custom_logger_handler

    format_string = '%(asctime)s | %(message)s'

    if filename:
        logging.basicConfig(filename=filename, format=format_string)

    level = __get_string_log_level(os.getenv("CUSTOM_LOG_LEVEL", "INFO"))

    __custom_logger = logging.getLogger("custom_log")
    __custom_logger_handler = logging.StreamHandler()
    setLevel(level) # MUST be called after setting the __custom_logger* variables, else infinite recursion!

    formatter = logging.Formatter(format_string)
    __custom_logger_handler.setFormatter(formatter)

    __custom_logger.addHandler(__custom_logger_handler)


def __get_string_log_level(level):
    if level == "DEBUG":
        return DEBUG
    elif level == "INFO":
        return INFO
    elif level == "WARNING":
        return WARNING
    elif level == "ERROR":
        return ERROR
    else:
        raise ValueError("'{level}' is not a recognised log level".format(level=level))


class LoggerConfigException(Exception):

    def __init__(self, message):
        Exception.__init__(self, message)