Logging utilities for Python projects

Version 5.0.0

This module provides ways of logging the input, output and errors in classes and functions It can be hooked up to graylog, printed to console or saved to a log file. It requires very little configuration.

Install

pip install loggo
# or
python setup.py install

Setup

Setting up the tool as you like requires a small amount of configuration. Put this in the main __init__.py, or in a file called log.py. so you can import the same, ready-set-up logger easily. Let's call our app tester, so you would use tester/__init__.py:

from loggo import Loggo
# All setup values are optional
setup = dict(facility='tester',             # name of program logging the message
             ip='0.0.0.0',                  # ip for graylog
             port=9999,                     # port for graylog
             do_print=True,                 # print to console
             do_write=True,                 # write to file
             logfile='mylog.txt',           # custom path to logfile
             line_length=200,               # line truncation for console logging
             truncation=1000,               # longest possible value in extra data
             private_data=['password'],     # list of sensitive args/kwargs
             obscured='[[[PRIVATE_DATA]]]') # string with which to obscure data
Loggo = Loggo(setup)

Usage

In other parts of the project, you should then be able to access the configured logger components with:

from tester import Loggo

Decorators

You can use @Loggo as a decorator on a class, class method or function. On classes, it will log every method; on methods and functions it will log the call signature, return and errors.

Furthermore, you can use @Loggo.ignore to ignore a particular method of a class decorated by @Loggo. There is also @Loggo.errors, which will only log errors, not calls and returns.

For an example use, let's make a simple class that multiplies two numbers, but only if a password is supplied. We can ignore logging of the boring authentication system.

@Loggo
class Multiplier(object):

    def __init__(self, base):
        self.base = base
        
    def multiply(self, n, password):
        """
        Multiply by the number given during initialisation--requires password
        """
        self.authenticated = self._do_authentication(password)
        if not self.authenticated:
            raise ValueError('Not authenticated!')
        return self.base * n

    @Loggo.ignore
    def _do_authentication(self, password):
        """Not exactly Fort Knox"""
        return password == 'tOpSeCrEt'

First, let's use it properly, with our secret password passed in:

mult = Multiplier(50)
result = mult.multiply(50, 'tOpSeCrEt')
assert result == 2500 # True

We'll get some nice text in the console:

11.05 2018 17:14:54 *Called Multiplier.multiply(n=50, password='[PRIVATE_DATA]')
11.05 2018 17:14:54 *Returned from Multiplier.multiply(n=50, password='[PRIVATE_DATA]') with int (2500)

Notice that our private argument password was successfully obscured. If you used do_write=True, this log will also be in your specified log file, also with password obscured.

result = Mult.multiply(7, 'password123')

An error will raise, a log will be generated and we'll get extra info in the console, including a traceback:

11.05 2018 17:19:43 *Called Multiplier.multiply(n=7, password='[PRIVATE_DATA]')
11.05 2018 17:19:43 *Errored during Multiplier.multiply(n=7, password='[PRIVATE_DATA]') with ValueError "Not authenticated!"    dev -- see below:
Traceback (most recent call last):
  File "/Users/danny/work/loggo/loggo/loggo.py", line 137, in full_decoration
    response = function(*args, **kwargs)
  File "tester.py", line 13, in multiply
    raise ValueError('Not authenticated!')
ValueError: Not authenticated!

@Loggo.events

@Loggo.events allows you to pass in messages for particular events:

@Loggo.events(
              called='Log string for method call',
              errored='Log string on exception',
              returned='Log string for return',
              error_level=50  # log level for errors
              )
def test():
    pass

Logging without decorators

For logging manually, Loggo provides methods similar to the logging functions of the logging standard library: Loggo.log, Loggo.debug, Loggo.info, Loggo.warning, Loggo.error, Loggo.critical. The methods use the configuration that has already been defined. The main method Loggo.log takes three parameters:

level = 50
msg = 'Message to log'
extra = dict(some='data', that='will', be='logged')
Loggo.log(level, msg, extra)
# console: 11.05 2018 17:36:24 Message to log  50
# extra_data in log file if `do_print` setting is True

Methods Loggo.debug, Loggo.info, Loggo.warning, Loggo.error and Loggo.critical are convenience methods for setting the log level. For instance,

Loggo.warning('A message', dict(some='data'))

is equivalent to

Loggo.log(logging.WARNING, 'A message', dict(some='data'))

where logging.WARNING is an integer constant imported from the standard library.

Methods

You can also start and stop logging with Loggo.start() and Loggo.stop(), at any point in your code, though error logs will still get through. If you want to suppress errors too, you can pass in allow_errors=False.

Context manager

You can suppress logs using a context manager. Errors are allowed here by default too:

with Loggo.pause(allow_errors=False):
    do_something()

Tests

python -m unittest

Bumping version

Version bumps should be done using the bump2version utility. Install it with pip:

pip install bump2version

Whenever you need to bump version, in the project root directory do:

bump2version (major | minor | patch)
git push <remote> <branch> --follow-tags

If you don't want to remember to use the --follow-tags flag, you can edit your git config:

git config --global push.followTags true

After this you can simply push the version bump commit to remote as you would normally, and the tag will also be pushed.

Limitations

Loggo uses Python's standard library (logging) to ultimately generate a log. There are some gotchas when using it: for instance, in terms of the extra data that can be passed in, key names for this extra data cannot clash with some internal names used within the logging module (message, args, etc.). To get around this, you'll get a warning that your data contains a bad key name, and it will be changed (i.e. from message to protected_message).