Flatten dict and vice versa

flatten.py

""" Flatten dict and vice versa

    Authored by: Fang Jiaan (fduodev@gmail.com)

    Example:

    >>> example = {'a': 1, 'b': {}, 'c': {'d': [], 'e': {'f': 0, 'h': u'xxx', 'i': {'j'}, 'k': object()}}}
    >>> flatten_dict(example) # doctest: +ELLIPSIS
    {'a': 1, 'b': {}, 'c.d': [], 'c.e.k': <object object at ...>, 'c.e.i': set(['j']), 'c.e.h': u'xxx', 'c.e.f': 0}
    >>> assert nestify_dict(flatten_dict(example)) == example
    >>> assert 'c.e.h' in flatten_dict(example)
    >>> assert flatten_dict(example)['c.e.h'] == example['c']['e']['h']

    >>> example2 = {'x.y': 1}
    >>> flatten_dict(example2) # doctest: +IGNORE_EXCEPTION_DETAIL
    Traceback (most recent call last):
    ValueError: Separator . already in key, this may lead unexpected behaviour, choose another.

"""
import collections


def flatten_dict(d, parent_key='', sep='.', quiet=False):
    items = []
    for k, v in d.items():

        if not quiet and sep in k:
            raise ValueError('Separator "%(sep)s" already in key, '
                             'this may lead unexpected behaviour, '
                             'choose another.' % dict(sep=sep))

        new_key = parent_key + sep + k if parent_key else k
        if isinstance(v, collections.MutableMapping):
            items.extend(flatten_dict(v, new_key, sep=sep).items())
            if not v:  # empty dict
                items.append((new_key, v))
        else:
            items.append((new_key, v))
    return dict(items)


def nestify_dict(d, sep='.'):
    ret = {}
    for k, v in d.items():
        if sep in k:
            keys = k.split(sep)
            target = ret

            while len(keys) > 1:
                current_key = keys.pop(0)
                target = target.setdefault(current_key, {})
            else:
                assert len(keys) == 1
                target[keys[0]] = v
        else:
            ret[k] = v
    return ret