Click-logging

Simple and beautiful logging for click applications

Project sources and documentation are available on Github

Documentation

Getting started

Assuming you have this Click application:

import click

@click.command()
def cli():
    click.echo("Dividing by zero.")

    try:
        1 / 0
    except ZeroDivisionError:
        click.echo("ERROR: Failed to divide by zero.")

Ignore the application's core functionality for a moment. The much more pressing question here is: How do we add an option to not print anything on success? We could try this:

import click

@click.command()
@click.option('--quiet', default=False, is_flag=True)
def cli(quiet):
    if not quiet:
        click.echo("Dividing by zero.")

    try:
        1 / 0
    except ZeroDivisionError:
        click.echo("ERROR: Failed to divide by zero.")

Wrapping if-statements around each echo-call is cumbersome though. And with that, we discover logging:

import logging
import click

logger = logging.getLogger(__name__)
# More setup for logging handlers here

@click.command()
@click.option('--quiet', default=False, is_flag=True)
def cli(quiet):
    if quiet:
        logger.setLevel(logging.ERROR)
    else:
        logger.setLevel(logging.INFO)
    # ...

Logging is a better solution, but partly because Python's logging module aims to be so generic, it doesn't come with sensible defaults for CLI applications. At some point you might also want to expose more logging levels through more options, at which point the boilerplate code grows even more.

This is where click-logging comes in:

import logging
import click
import click_logging

logger = logging.getLogger(__name__)
click_logging.basic_config(logger)

@click.command()
@click_logging.simple_verbosity_option(logger)
def cli():
    logger.info("Dividing by zero.")

    try:
        1 / 0
    except ZeroDivisionError:
        logger.error("Failed to divide by zero.")

The output will look like this:

Dividing by zero.
error: Failed to divide by zero.

The error:-prefix will be red, unless the output is piped to another command.

The simple_verbosity_option decorator adds a --verbosity option that takes a (case-insensitive) value of DEBUG, INFO, WARNING, ERROR, or CRITICAL, and calls setLevel on the given logger accordingly.

note

Make sure to define the simple_verbosity_option as early as possible. Otherwise logging setup will not be early enough for some of your other eager options.

Customize output

You can customize click styles for each log level with style_kwargs keyword argument of basic_config function.

import logging
import click_logging

logger = logging.getLogger(__name__)
style_kwargs = {
    'error': dict(fg='red', blink=True),
    'exception': dict(fg='red', blink=True),
    'critical': dict(fg='red', blink=True)
}
click_logging.basic_config(logger, style_kwargs=style_kwargs)

You can customize click echo for each log level using echo_kwargs keyword argument of basic_config function.

import logging
import click_logging

logger = logging.getLogger(__name__)
echo_kwargs = {
    'error': dict(err=True),
    'exception': dict(err=True),
    'critical': dict(err=True),
}
click_logging.basic_config(logger, echo_kwargs=True)

Fork

This is a fork of click-contrib/click-log

Motivations of the fork:

• semantic-release and github actions to merge and release often.
• more configuration options.

License

Licensed under the MIT, see LICENSE.

Changelog

v1.0.1 (2021-01-06)

Fix

• Add missing string interpolation in error message (3de6f06)
• help: Add trailing dot to help text (1ed426f)

Documentation

• readme: Enhance README.md formatting (3507ba3)

v1.0.0 (2021-01-06)

Feature

• customize: Add more customization capabilities in basic_config (621c0a2)

Breaking

• click_log has been renamed to click_logging (f4a8ddf)