Python descriptor for attribute-like access in dict subclasses

dict_item.py

class dict_item:
    """
    Create an attribute in a custom dict subclass that accesses
    the dict value keyed by the attribute's name:
    
        >>> class UserInfo(dict):
        >>>     name = dict_item()
        >>>     age = dict_item()
        >>> user = UserInfo(name="John")
        >>> print(user.name)
        John
        >>> user.age = 42
        >>> user["color"] = "green"
        >>> print(user)
        {"name":"John", "age": 42, "color": "green"}

    `user` acts as a normal dictionary, but the items under keys "name" and "age"
    can be accessed as attributes too.

    `dict_item` allows to easily create/prototype dict-based data structures
    that have some predefined (but possibly missing) fields as attributes.
    This makes the data structure more self-documenting than a regular dict
    and helps avoiding key typo's (e.g. through code completion features in your
    editor or IDE).

    This class implements the descriptor protocol.
    """

    def __set_name__(self, owner, name):
        self.key = name

    def __get__(self, instance, owner):
        return instance[self.key]

    def __set__(self, instance, value):
        instance[self.key] = value