dinges.py

from collections.abc import Mapping


class DictView(Mapping):
    # sentinel value used to check when a KeyError should be raised rather than returning a value
    _no_default = object()

    def __init__(self, source, separator='.'):
        self._source = source
        self._separator = separator

    def get(self, key, default=None):
        try:
            value = self._source
            for step in key.split(self._separator):
                value = value[step]

            if isinstance(value, dict):
                return DictView(value)
            else:
                return value
        except KeyError:
            return default
        except TypeError:
            return default

    def __len__(self):
        return len(self._source)

    def __iter__(self):
        return iter(self._source)

    def __contains__(self, item):
        return self.get(item) is not None

    def __getitem__(self, item):
        value = self.get(item, self._no_default)
        if value is self._no_default:
            raise KeyError(item)
        else:
            return value

    def __str__(self):
        return str(self._source)