Merges result of function or attribute from child class with result of function or attribute from the base class.

mergewithbase.py

class merge_with_base(object):
    """
    Merges result of function or attribute from child class with result of
    function or attribute from the base class.

    :param type: Use this base class instead of first base class found and
                 not with mixins

    .. note::

        Currently it only works with one base class

    >>> class parent(object):
    ...     def test(self, param):
    ...         return param + [False]
    ...
    >>> class child(parent):
    ...     @merge_with_base()
    ...     def test(self, param):
    ...         return param + [False]
    >>> child().test(["test"])
    ['test', False, 'test', False]

    It also works with properties:

    >>> class parent(object):
    ...     @property
    ...     def test(self):
    ...         return [False]
    ...
    >>> class child(parent):
    ...     @property
    ...     @merge_with_base()
    ...     def test(self):
    ...         return [True]
    >>> child().test
    [False, True]

    """

    def __init__(self, type=None):
        self.type = type

    def __call__(self, obj):
        @wraps(obj)
        def merger(*args, **kwargs):
            base = args[0].__class__.__bases__[0] or self.type
            f = getattr(args[0].__class__.__bases__[0], obj.func_name, None)
            args = (super(base, args[0]),) + args[1:]

            if ismethod(f):
                ret = f.im_func(*args, **kwargs)
            elif isinstance(f, property):
                ret = f.fget(*args, **kwargs)
            else:
                ret = None

            return ret + obj(*args, **kwargs) if ret else obj(*args, **kwargs)
        return merger

if __name__ == "__main__":
    import doctest
    doctest.testmod()