Recursive DotDict

The accepted answer has some gotchas, such as failing on hasattr(). Using the keys to simulate properties means you need to do a tad more than assign __getattr__ = dict.__getitem__. Here’s a more robust implementation with tests:

from collections import OrderedDict, Mapping

class DotDict(OrderedDict):
    '''
    Quick and dirty implementation of a dot-able dict, which allows access and
    assignment via object properties rather than dict indexing.
    '''

    def __init__(self, *args, **kwargs):
        # we could just call super(DotDict, self).__init__(*args, **kwargs)
        # but that won't get us nested dotdict objects
        od = OrderedDict(*args, **kwargs)
        for key, val in od.items():
            if isinstance(val, Mapping):
                value = DotDict(val)
            else:
                value = val
            self[key] = value

    def __delattr__(self, name):
        try:
            del self[name]
        except KeyError as ex:
            raise AttributeError(f"No attribute called: {name}") from ex

    def __getattr__(self, k):
        try:
            return self[k]
        except KeyError as ex:
            raise AttributeError(f"No attribute called: {k}") from ex

    __setattr__ = OrderedDict.__setitem__

And the tests:

class DotDictTest(unittest.TestCase):
    def test_add(self):
        exp = DotDict()

        # test that it's not there
        self.assertFalse(hasattr(exp, 'abc'))
        with self.assertRaises(AttributeError):
            _ = exp.abc
        with self.assertRaises(KeyError):
            _ = exp['abc']

        # assign and test that it is there
        exp.abc = 123
        self.assertTrue(hasattr(exp, 'abc'))
        self.assertTrue('abc' in exp)
        self.assertEqual(exp.abc, 123)

    def test_delete_attribute(self):
        exp = DotDict()

        # not there
        self.assertFalse(hasattr(exp, 'abc'))
        with self.assertRaises(AttributeError):
            _ = exp.abc

        # set value
        exp.abc = 123
        self.assertTrue(hasattr(exp, 'abc'))
        self.assertTrue('abc' in exp)
        self.assertEqual(exp.abc, 123)

        # delete attribute
        delattr(exp, 'abc')

        # not there
        self.assertFalse(hasattr(exp, 'abc'))
        with self.assertRaises(AttributeError):
            delattr(exp, 'abc')

    def test_delete_key(self):
        exp = DotDict()

        # not there
        self.assertFalse('abc' in exp)
        with self.assertRaises(KeyError):
            _ = exp['abc']

        # set value
        exp['abc'] = 123
        self.assertTrue(hasattr(exp, 'abc'))
        self.assertTrue('abc' in exp)
        self.assertEqual(exp.abc, 123)

        # delete key
        del exp['abc']

        # not there
        with self.assertRaises(KeyError):
            del exp['abc']

    def test_change_value(self):
        exp = DotDict()
        exp.abc = 123
        self.assertEqual(exp.abc, 123)
        self.assertEqual(exp.abc, exp['abc'])

        # change attribute
        exp.abc = 456
        self.assertEqual(exp.abc, 456)
        self.assertEqual(exp.abc, exp['abc'])

        # change key
        exp['abc'] = 789
        self.assertEqual(exp.abc, 789)
        self.assertEqual(exp.abc, exp['abc'])

    def test_DotDict_dict_init(self):
        exp = DotDict({'abc': 123, 'xyz': 456})
        self.assertEqual(exp.abc, 123)
        self.assertEqual(exp.xyz, 456)

    def test_DotDict_named_arg_init(self):
        exp = DotDict(abc=123, xyz=456)
        self.assertEqual(exp.abc, 123)
        self.assertEqual(exp.xyz, 456)

    def test_DotDict_datatypes(self):
        exp = DotDict({'intval': 1, 'listval': [1, 2, 3], 'dictval': {'a': 1}})
        self.assertEqual(exp.intval, 1)
        self.assertEqual(exp.listval, [1, 2, 3])
        self.assertEqual(exp.listval[0], 1)
        self.assertEqual(exp.dictval, {'a': 1})
        self.assertEqual(exp.dictval['a'], 1)
        self.assertEqual(exp.dictval.a, 1)  # nested dotdict works

And just for fun, you can turn an object into a DotDict with this:

def to_dotdict(obj):
    ''' Converts an object to a DotDict '''
    if isinstance(obj, DotDict):
        return obj
    elif isinstance(obj, Mapping):
        return DotDict(obj)
    else:
        result = DotDict()
        for name in dir(obj):
            value = getattr(obj, name)
            if not name.startswith('__') and not inspect.ismethod(value):
                result[name] = value
        return result

I’ve been slightly unhappy with all the different answers I have found to this problem. My goals in my implementation were:
1) Don’t create more new object attributes than necessary.
2) Don’t allow overwriting access to built-in attributes.
3) The class converts added items to maintain consistency.

class attrdict(dict):
    """
    Attribute Dictionary.

    Enables getting/setting/deleting dictionary keys via attributes.
    Getting/deleting a non-existent key via attribute raises `AttributeError`.
    Objects are passed to `__convert` before `dict.__setitem__` is called.

    This class rebinds `__setattr__` to call `dict.__setitem__`. Attributes
    will not be set on the object, but will be added as keys to the dictionary.
    This prevents overwriting access to built-in attributes. Since we defined
    `__getattr__` but left `__getattribute__` alone, built-in attributes will
    be returned before `__getattr__` is called. Be careful::

        >>> a = attrdict()
        >>> a['key'] = 'value'
        >>> a.key
        'value'
        >>> a['keys'] = 'oops'
        >>> a.keys
        <built-in method keys of attrdict object at 0xabcdef123456>

    Use `'key' in a`, not `hasattr(a, 'key')`, as a consequence of the above.
    """
    def __init__(self, *args, **kwargs):
        # We trust the dict to init itself better than we can.
        dict.__init__(self, *args, **kwargs)
        # Because of that, we do duplicate work, but it's worth it.
        for k, v in self.iteritems():
            self.__setitem__(k, v)

    def __getattr__(self, k):
        try:
            return dict.__getitem__(self, k)
        except KeyError:
            # Maintain consistent syntactical behaviour.
            raise AttributeError(
                "'attrdict' object has no attribute '" + str(k) + "'"
            )

    def __setitem__(self, k, v):
        dict.__setitem__(self, k, attrdict.__convert(v))

    __setattr__ = __setitem__

    def __delattr__(self, k):
        try:
            dict.__delitem__(self, k)
        except KeyError:
            raise AttributeError(
                "'attrdict' object has no attribute '" + str(k) + "'"
            )

    @staticmethod
    def __convert(o):
        """
        Recursively convert `dict` objects in `dict`, `list`, `set`, and
        `tuple` objects to `attrdict` objects.
        """
        if isinstance(o, dict):
            o = attrdict(o)
        elif isinstance(o, list):
            o = list(attrdict.__convert(v) for v in o)
        elif isinstance(o, set):
            o = set(attrdict.__convert(v) for v in o)
        elif isinstance(o, tuple):
            o = tuple(attrdict.__convert(v) for v in o)
        return o

Shamelessly plugging my own package

There is a package doing exactly what you want and also something more and it is called Prodict.

from prodict import Prodict

life_dict = {'bigBang':
                {'stars':
                    {'planets': []}
                }
            }

life = Prodict.from_dict(life_dict)

print(life.bigBang.stars.planets)
# prints []

# you can even add new properties dynamically
life.bigBang.galaxies = []

PS 1: I’m the author of the Prodict.

PS 2: This is a direct copy paste of an answer of another question.