Modified Python Dotdictify

dotdictify.py

# turn dict into an object that allows access to nested keys via dot notation
# from http://stackoverflow.com/questions/3797957/python-easily-access-deeply-nested-dict-get-and-set
# made three modifications:
#   --added `get()` method
#   --added `if not dict.__contains__...` to `__contains__()`
#   --can now accept None as key
class dotdictify(dict):
    def __init__(self, value=None):
        if value is None:
            pass
        elif isinstance(value, dict):
            for key in value:
                print key
                self.__setitem__(key, value[key])
        else:
            raise TypeError, 'expected dict'

    def __setitem__(self, key, value):
        if key is not None and '.' in key:
            myKey, restOfKey = key.split('.', 1)
            target = self.setdefault(myKey, dotdictify())
            if not isinstance(target, dotdictify):
                raise KeyError, 'cannot set "%s" in "%s" (%s)' % (restOfKey, myKey, repr(target))
            target[restOfKey] = value
        else:
            if isinstance(value, dict) and not isinstance(value, dotdictify):
                value = dotdictify(value)
            dict.__setitem__(self, key, value)

    def __getitem__(self, key):
        if key is None or '.' not in key:
            return dict.__getitem__(self, key)
        myKey, restOfKey = key.split('.', 1)
        target = dict.__getitem__(self, myKey)
        if not isinstance(target, dotdictify):
            raise KeyError, 'cannot get "%s" in "%s" (%s)' % (restOfKey, myKey, repr(target))
        return target[restOfKey]

    def __contains__(self, key):
        if key is None or '.' not in key:
            return dict.__contains__(self, key)
        myKey, restOfKey = key.split('.', 1)
        if not dict.__contains__(self, myKey):
            return False
        target = dict.__getitem__(self, myKey)
        if not isinstance(target, dotdictify):
            return False
        return restOfKey in target

    def setdefault(self, key, default):
        if key not in self:
            self[key] = default
        return self[key]

    def get(self, k, d=None):
        if dotdictify.__contains__(self, k):
            return dotdictify.__getitem__(self, k)
        return d

    __setattr__ = __setitem__
    __getattr__ = __getitem__

Suggestion:

Line 32: return dict.getitem(self, key)
Replace with: return dict.get(self, key, None)

Line 34: target = dict.getitem(self, myKey)
Replace with: target = dict.get(self, myKey, None)

Suggestion from @d0o0b is not good (at least for me), I got many "NoneType" related errors with those lines.
Instead I extended the nested behavior to elements inside lists:

elif isinstance(value, list):
    value = [dotdictify(x) if isinstance(x, dict) and not isinstance(value, dotdictify) else x for x in value]

this lets me access mongoDB documents using dot notation and save them directly. Thanks @einnocent!