Example of configurator which shows cross-referencing between different parts of the configuration + access to data in external modules.

configurator.py

#
# Copyright (C) 2013 Vinay Sajip. All rights reserved.
#

import re
import sys
import unittest

from distlib.util import Configurator

class TestContainer(object):
    def __init__(self, *args, **kwargs):
        self.args = args
        self.kwargs = kwargs

class ConfigTestCase(unittest.TestCase):
    def test_basic(self):
        d = {
            'a': 1,
            'b': 2.0,
            'c': 'xyz',
            'stderr': 'ext://sys.stderr',
            'list_o_stuff': [
                'cfg://stderr',
                'ext://sys.stdout',
                'ext://logging.NOTSET',
            ],
            'dict_o_stuff': {
                'k1': 'cfg://list_o_stuff[1]',
                'k2': 'abc',
                'k3': 'cfg://list_o_stuff',
            },
            'another_dict_o_stuff': {
                'k1': 'cfg://dict_o_stuff[k2]',
                'k2': 'ext://re.I',
                'k3': 'cfg://dict_o_stuff[k3][0]',
            },
            'custom': {
                '()': '__main__.TestContainer',
                '[]': [1, 'a', 2.0, ('b', 'c', 'd')],
                '.': {
                    'p1': 'a',
                    'p2': 'b',
                    'p3': {
                        '()' : '__main__.TestContainer',
                        '[]': [1, 2],
                        '.': {
                            'p1': 'c',
                        },
                    },
                },
                'k1': 'v1',
                'k2': 'v2',
            }
        }

        cfg = Configurator(d)
        self.assertEqual(cfg['a'], 1)
        self.assertEqual(cfg['b'], 2.0)
        self.assertEqual(cfg['c'], 'xyz')
        self.assertTrue(cfg['stderr'] is sys.stderr)
        self.assertTrue(cfg['list_o_stuff'][0] is sys.stderr)
        self.assertTrue(cfg['list_o_stuff'][1] is sys.stdout)
        self.assertEqual(cfg['list_o_stuff'][-1], 0)
        self.assertTrue(cfg['dict_o_stuff']['k1'] is sys.stdout)
        self.assertEqual(cfg['another_dict_o_stuff']['k1'], 'abc')
        self.assertTrue(cfg['another_dict_o_stuff']['k2'] is re.I)
        self.assertTrue(cfg['another_dict_o_stuff']['k3'] is sys.stderr)
        custom = cfg['custom']
        self.assertTrue(isinstance(custom, TestContainer))
        self.assertEqual(custom.args, (1, 'a', 2.0, ('b', 'c', 'd')))
        self.assertEqual(custom.kwargs, {'k1': 'v1', 'k2': 'v2'})
        self.assertEqual(custom.p1, 'a')
        self.assertEqual(custom.p2, 'b')
        self.assertTrue(isinstance(custom.p3, TestContainer))
        self.assertEqual(custom.p3.args, (1, 2))
        self.assertEqual(custom.p3.kwargs, {})
        self.assertEqual(custom.p3.p1, 'c')

if __name__ == '__main__':
    unittest.main()