logquacious 0.3.0

Logging utilities to help you over-communicate

logquacious

Logquacious is a set of simple logging utilities to help you over-communicate. (Logorrhea would’ve been a good name, if it didn’t sound so terrible.)

Good application logging is easy to overlook, until you have to debug an error in production. Logquacious aims to make logging as easy as possible.

Quick start

To get started, first make sure logquacious is installed:

$ pip install logquacious

You’ll also need to set up logging for your application. For this example, we’ll use a really simple configuration:

import logging

logging.basicConfig(format='%(levelname)s: %(message)s', level=logging.DEBUG)

The main interface to logquacious is the LogManager, which can be used for normal logging:

import logquacious

log = logquacious.LogManager(__name__)

log.debug('Nothing to see here.')

Due to our simplified logging format defined earlier, that would output:

DEBUG: Nothing to see here.

That isn’t a very interesting example. In addition to basic logging, LogManager has a context attribute for use as a context manager:

>>> with log.context.debug('greetings'):
...    print('Hello!')
DEBUG: Enter greetings
Hello!
DEBUG: Exit greetings

The same attribute can be used as a decorator, as well:

@log.context.info
def divide(numerator, denominator):
    if denominator == 0:
        log.warning('Attempted division by zero. Returning None')
        return None
    return numerator / denominator

>>> divide(1, 0)
INFO: Call `divide()`
WARNING: Attempted division by zero. Returning None
INFO: Return from `divide`

Even better, you can log input arguments as well:

@log.context.info(show_args=True, show_kwargs=True)
def greet(name, char='-'):
    msg = 'Hello, {name}!'.format(name=name)
    print(msg)
    print(char * len(msg))

>>> greet('Tony', char='*')
INFO: Call `greet('Tony', char='*')`
Hello, Tony!
************
INFO: Return from `greet`

There’s also a special context manager for suppressing errors and logging:

with log.and_suppress(ValueError, msg="It's ok, mistakes happen"):
    raise ValueError('Test error')

[ERROR] It's ok, mistakes happen
Traceback (most recent call last):
  File "/Users/tyu/code/logquacious/logquacious/log_manager.py", line 103, in and_suppress
    yield
  File "scripts/example.py", line 26, in <module>
    raise ValueError('Test error')
ValueError: Test error

Configuration

The message templates used by LogManager.context can be configured to your liking by passing a context_templates argument to LogManager:

log = logquacious.LogManager(__name__, context_templates={
    'context.start': '=============== Enter {label} ===============',
    'context.finish': '=============== Exit {label} ===============',
})

with log.context.debug('greetings'):
    print('Hello!')

[DEBUG] =============== Enter greetings ===============
Hello!
[DEBUG] =============== Exit greetings ===============

The general format for context_templates keys is:

[CONTEXT_TYPE.]('start'|'finish')[.LOG_LEVEL_NAME]

where square-brackes marks optional fields.

CONTEXT_TYPE can be any of the following:

• function: Template used when called as a decorator.

• context: Template used when called as a context manager.

LOG_LEVEL_NAME can be any of the following logging levels:

• DEBUG

• INFO

• WARNING

• ERROR

• CRITICAL

For example, consider the cascade graph for function.start.DEBUG, which looks like:

     function.start.DEBUG
          /       \
start.DEBUG       function.start
          \       /
            start

The cascade is performed using a breadth-first search. If function.start.DEBUG is not defined, check start.DEBUG then check function.start BEFORE checking start.

Credits

This package was created with Cookiecutter and the audreyr/cookiecutter-pypackage project template.

History

0.3.0 (2018-10-05)

• Add decorator support for log.and_suppress and log.and_reraise context managers

• Suppress logging for null/empty log message templates

0.2.0 (2018-10-03)

Changed default templates. In 0.1.0, the templates were:

DEFAULT_TEMPLATES = {
    'start': 'Start {label}',
    'finish': 'Finish {label}',
}

These defaults have been changed to:

DEFAULT_TEMPLATES = {
    'start': 'Enter {label}',
    'finish': 'Exit {label}',
    'function.start': 'Call `{label}({arguments})`',
    'function.finish': 'Return from `{label}`',
}

0.1.0 (2018-10-03)

• First release on PyPI.