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Yet another python logger that simplifies json file logging and prettifies console output

Project description

LazyLog

Build Status Documentation Status

Yet another python logger that aims to:

  • Simplify logging setup - down to config and a single line
  • Be minimal - single file, no dependencies
  • Support console and file logging with different log levels, different format and file rotation out of the box
  • Prettify an align console output to be more human readable
  • Allow for easy JSON logging (TODO)
  • "Fix some issues" of the default logging facility:
    • Handles new-lines in messages by either re-adding the preamble or escaping the new-line characters
    • Adds color to the console, based on the log level
    • Prettifies basic structures (list, dicts and tuples)
    • Handles logfile permissions for multi-user deployments
    • Supports easy logger mocking (into StringIO)

Install

You can install this lib via pip:

pip install lazylog

or you can just download the code in your project:

curl https://raw.githubusercontent.com/urban-1/lazylog/master/lazylog/__init__.py > /path/to/lazylog.py

Usage

NOTE: For pretty colors on this README please visit the readthedocs version

NOTE2: You can find all the sources of this section in examples folder

Basics

In the simplest form, you can initialize lazylog with:

# Import the Logger class
from lazylog import Logger

# Initialize with all defaults
Logger.init()

This creates a console-only logger with all the values set to their defaults:

{
   'color': True,
   'splitLines': True,
   'level': logging.DEBUG,
   'pretty': True
}
  • color: Instructs lazylog to use different colors for different levels
  • splitLines: Enables handling new-lines by re-printing the preamble on every line
  • level: As usual, sets the logging level for the terminal
  • pretty: Enables prettifying dicts, lists and tuples to be more readable

Once initialized you can use the logging module as usual - nothing special:

logging.debug("This is an example log line")
logging.info("This logger handles\nNew\nLines")
logging.warning({"also": "handles basic structures", "like": list("lists"), "and": ("colors", "!")})
logging.error("Errors stick out")
logging.critical("but critical sticks out more...")

The output should look like:

08-05-2018 21:40:16.943 13859:139943539918656 DEBUG            console 17  : This is an example log line
08-05-2018 21:40:16.943 13859:139943539918656 INFO             console 18  : This logger handles
08-05-2018 21:40:16.943 13859:139943539918656 INFO             console 18  : New
08-05-2018 21:40:16.943 13859:139943539918656 INFO             console 18  : Lines
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  : (dict) {
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :    'and': (
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :            'colors',
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :            '!'
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :    ),
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :    'like': [
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :            'l',
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :            'i',
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :            's',
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :            't',
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :            's'
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :    ],
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  :    'also': 'handles basic structures'
08-05-2018 21:40:16.943 13859:139943539918656 WARNING          console 19  : }
08-05-2018 21:40:16.943 13859:139943539918656 ERROR            console 20  : Errors stick out
08-05-2018 21:40:16.943 13859:139943539918656 CRITICAL         console 21  : but critical sticks out more...

Customizing

You can customize lazylog and disable any of the features you don't like, so

# Init
termSpecs = {"level": logging.DEBUG, "splitLines": False, "pretty": False }
Logger.init(LOGDIR, termSpecs=termSpecs)

# Use ...
logging.debug("You can remove all the fancy stuff:")
logging.info("... keeping\n each message\n in its own line")
logging.warning({"and": "flatten structures", "like": list("lists")})

gives you:

08-05-2018 21:19:40.688 11639:140599510849344 DEBUG    console_customi 18  : You can remove all the fancy stuff:
08-05-2018 21:19:40.689 11639:140599510849344 INFO     console_customi 19  : ... keeping\n each message\n in its own line
08-05-2018 21:19:40.689 11639:140599510849344 WARNING  console_customi 20  : {'like': ['l', 'i', 's', 't', 's'], 'and': 'flatten structures'}

... while initializing with:

termSpecs = {"level": logging.DEBUG, "splitLines": True, "pretty": False }

gives you:

08-05-2018 21:30:05.312 12648:140218785630016 ERROR    console_customi 25  : However,
08-05-2018 21:30:05.312 12648:140218785630016 ERROR    console_customi 25  : You can choose to split
08-05-2018 21:30:05.312 12648:140218785630016 ERROR    console_customi 25  : lines
08-05-2018 21:30:05.312 12648:140218785630016 CRITICAL console_customi 26  : ['but', 'not', 'prettify\nstructs']

Of course you can disable everything, falling back to the default logging behaviour with the only difference being the log format:

08-05-2018 21:30:05.312 12648:140218785630016 INFO     console_customi 31  : Boooriiiing

Finally, in the init() function you can override the default format and date format by passing fmt and datefmt parameters. The defaults are:

DATEFORMAT = '%d-%m-%Y %H:%M:%S'
LOGFORMAT = '%(asctime)s.%(msecs)03d %(process)s:%(thread)u %(levelname)-8s %(module)15.15s %(lineno)-4s: %(message)s'

Files

In case where you (the developer) are not the one running the code, you most probably need a log-file! If your application is a CLI one, probably the end-user should not be seeing all the debugging info, but warnings and errors only. Python logging facility supports multiple handlers working simultaneously and lazylog allows you to use this feature hassle-free. To define a file logger do:

termSpecs = {"level": logging.DEBUG}
fileSpecs = [{"filename": LOGFILE, "level":logging.DEBUG}]
Logger.init(LOGDIR, termSpecs=termSpecs, fileSpecs=fileSpecs)

The above creates a file in LOGDIR/LOGFILE with the default settings which are:

    {
        'format': 'console'
        'backupCount': 20
        'maxBytes': 10000000 # 10MB
        'color': False,
        'splitLines': True,
        'pretty': False
    }
  • backupCount: Is the number of files we keep
  • maxBytes: Is the maximum file size, after which rotation takes place
  • format: Controls which LogFormatter is being used. By default the ColorFormatter is used and thus the options color, splitLines and pretty are also supported. Other values include: default and json which we will see later on

The above settings produce the following output in the file:

08-05-2018 15:57:24.118 16142:140509479982912 DEBUG            logfile 23  : ^---same as console, this is an example log line
08-05-2018 15:57:24.118 16142:140509479982912 INFO             logfile 24  : This logger handles
08-05-2018 15:57:24.118 16142:140509479982912 INFO             logfile 24  : New
08-05-2018 15:57:24.118 16142:140509479982912 INFO             logfile 24  : Lines
08-05-2018 15:57:24.119 16142:140509479982912 WARNING          logfile 25  : {'but': 'Flattens structs by default'}
08-05-2018 15:57:24.119 16142:140509479982912 ERROR            logfile 26  : Errors DONT stick out - color is not used

with splitLines: False you get:

# Code:
# logging.info("Like console\nYou can avoid\nsplitting lines")

08-05-2018 15:57:24.119 16142:140509479982912 INFO             logfile 42  : Like console\nYou can avoid\nsplitting lines

while with pretty: True you get:

# Code:
# logging.info({"or": "enable prettifying!"})

08-05-2018 15:57:24.120 16142:140509479982912 INFO             logfile 55  : (dict) {
08-05-2018 15:57:24.120 16142:140509479982912 INFO             logfile 55  :    'or': 'enable prettifying!'
08-05-2018 15:57:24.120 16142:140509479982912 INFO             logfile 55  : }

JSON format

JSON logging is most useful when we need to index our logs to a database or stream them and generally for machine-to-machine communication. At the moment, lazylog does not support JSON logging on the terminal but does support it for files. To enable it, initialize with:

fileSpecs = [{"filename": LOGFILE, "level":logging.DEBUG, "format":"json"}]

The following ways of logging are supported:

logging.info("Simple str message")
logging.warning("Message with metadata", extra={"user": "nwj12"})
logging.debug({"what": "dict-based logging"}, extra={"user": "asd32"})
logging.info(["anything", "json", "serializable", "see OBJECT"], extra={"foo":"bar"})

and the results will be (each one in a single line in the logfile):

{
    "filename": "logfile.py",
    "module": "logfile",
    "timestamp": 1525799704.8904743,
    "message": "Simple str message",
    "thread": 140193498228544,
    "levelname": "INFO",
    "process": 27529
}

{
    "filename": "logfile.py",
    "user": "nwj12",
    "module": "logfile",
    "timestamp": 1525799704.890644,
    "message": "Message with metadata",
    "thread": 140193498228544,
    "levelname": "WARNING",
    "process": 27529
}

{
    "filename": "logfile.py",
    "user": "asd32",
    "module": "logfile",
    "what": "dict-based logging",
    "timestamp": 1525799704.8907733,
    "message": "",
    "process": 27529,
    "levelname": "DEBUG",
    "thread": 140193498228544
}

{
    "filename": "logfile.py",
    "timestamp": 1525799704.8909438,
    "module": "logfile",
    "thread": 140193498228544,
    "foo": "bar",
    "message": "",
    "process": 27529,
    "levelname": "INFO",
    "object": [
        "anything",
        "json",
        "serializable",
        "see OBJECT"
    ]
}

Finally, one can have multiple log files with different formats and log levels. This can be done either on initialization state, or later on with addFileLogger method:

# On init:
fileSpecs = [
    {"filename": LOGFILE, "level":logging.DEBUG, "format":"json"},
    {"filename": LOGFILE2, "level":logging.INFO}
]
Logger.init(LOGDIR, termSpecs=termSpecs, fileSpecs=fileSpecs)

# Later-on:
fileSpecs2 = {"filename": LOGFILE2, "level":logging.INFO}
Logger.addFileLogger(fileSpecs2)

Default format

I would really not suggest this... but you get

# Code:
# logging.info("You\n can set the \n format to\n default")
# logging.warning("But I don't like it...")

08-05-2018 15:57:24.120 16142:140509479982912 INFO             logfile 70  : You
 can set the
 format to
 default
08-05-2018 15:57:24.120 16142:140509479982912 WARNING          logfile 71  : But I don't like it...

Acknowledgements

This project has been put together by bits and pieces of code over fairly long time (and "as required"). I have rewritten lots of parts, cleaned up and packaged it in a reusable form. However, lots of other people's code is included and as you will see in the comments in the source, credit is given when applicable. Just to mention some (for the ones that will not read the source):

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