a no frills config module

config.py

"""A no frills config module.

A global config is encapsulated at the module level.

This module automatically looks for a config.json
in the project root when it is imported, and will
bootstrap the config with it if found.


# main.py

import config

config.bootstrap(some_data)
config.set('time', time.time())

----------

# module.py

import config

db = config.get('db_connection_string')

----------

You can bootstrap the config with a json string,
python dict, path to file, or file-like object.
"""

from __future__ import print_function

import json
import os


class Config(object):
    """Class for containing configuration."""

    def get(self, key, default=None):
        """Get key from object."""
        return getattr(self, key, default)

    def set(self, key, value):
        """Set key with value."""
        return setattr(self, key, value)

    def clear(self):
        for key in vars(self).keys():
            if isinstance(key, basestring):
                delattr(self, key)
        return self

    def __repr__(self):
        return '<Config at {}: {}>'.format(
            hex(id(self)), list(vars(self).keys()))


_CONFIG = Config()


def get(key, default=None):
    """Get key from current config object."""
    return _CONFIG.get(key, default)


def set(key, value):
    """Get key from current config object."""
    return _CONFIG.set(key, value)


def clear():
    """Clear all options from the current config object."""
    return _CONFIG.clear()


def load():
    """Return current config object."""
    return _CONFIG


def pprint():
    return json.dumps(vars(load()), indent=2, sort_keys=2)


def bootstrap(data):
    """Load data into current config object.

    This function is idempotent, and will
    update the existing config if bootstrapped
    multiple times.

    Argument can be a local path to a json file,
    an open file-like object with a read() method,
    a json string to deserialize, or a python mapping
    with an items() method.
    """
    if isinstance(data, basestring) and os.path.isfile(data):
        # path to local file
        with open(data, 'r') as _d:
            data = json.load(_d)
    elif callable(getattr(data, 'read', None)):
        # file-like object
        data = json.load(data)
    elif isinstance(data, basestring):
        # only do this if its not already a python mapping
        data = json.loads(data)
    _cfg = load()
    for key, value in data.items():
        _cfg.set(key, value)
    return _cfg


_config_file = os.path.realpath(
    os.path.join(os.path.dirname(os.path.realpath(__file__)),
    os.path.pardir, 'config.json')
)
if os.path.isfile(_config_file):
    bootstrap(_config_file)

For use with https://github.com/mitsuhiko/click, add this to the bottom of config,py

import click


def _click_load(ctx, param, value):
    bootstrap(value)

click_option = click.option(
    '--config-file', '-c',
    callback=_click_load,
    default='path/to/config.json',
    show_default=True,
    expose_value=False,
)

and in your cli module, something like this works:

import config

@click.group()
@config.click_option
def click_group():
    pass