Pass kwargs defined on class to class initialization

initkwargs.py

def DefaultKwargs(**init_kwargs):
  """Decorator factory for passing default kwargs to the decorated function.

  Returns:
    decorator function
  """

  def decorator(func):
    """Recieves a function, then wraps it with wrapper_func

    args:
      func: callable function or method

    returns:
      func wrapped inside wrapper_func
    """

    def wrapper_func(*args, **kwargs):
      """This is the outer wrapper of the function that was passed to decorator.

        The args are passed untouched to the wrapped function.  
        The kwargs are used to update a copy of the initial kwargs that were 
        passed to the decorator.
      """
      combo_kwargs = {}
      combo_kwargs.update(init_kwargs)
      combo_kwargs.update(kwargs)

      func(*args, **combo_kwargs)

    return wrapper_func
  return decorator

class InitKwargsBase(type):
  """ Metaclass to pass kwargs defined on a class to initialization.

      The key word arguments(kwargs) are defined 
      on a child class using this format:

        class Parent(InitKwargs):

          class InitKwarg:
            key_word1 = 'value'
            key_word2 = 'value2'

        Parent's __init__(**kwargs) function will receive:
          combo_kwargs = {}
          combo_kwargs.update(init_kwargs)
          combo_kwargs.update(kwargs)

          where init_kwargs = {'key_word1':'value', 'key_word2':'value2'}

      A class factory(metaclass) wraps the init function and stores 
      the kwargs to pass at initialization time.

      Altering InitKwargs on the class during runtime will have no effect. 
      The kwargs are stored in the closure of the init decorator, 
      when the class object is created.

      The kwargs directly passed to __init__ override any defined on 
      the class.
  """

  def __init__(cls, name, bases, dct):
    super(InitKwargsBase, cls).__init__(name, bases, dct)

    kwargs_cls = getattr(cls, 'InitKwargs', None)
    if kwargs_cls:
      kwargs = {}
      for name in dir(kwargs_cls):
        if not name.startswith('__'):
          kwargs[name] = getattr(kwargs_cls, name)

      init = cls.__init__
      cls.__init__ = DefaultKwargs(**kwargs)(init)


class InitKwargs(object):
  """Class to pass kwargs defined on a class to initialization

  See the metaclass, InitKwargsBase, for further details.

  """
  __metaclass__ = InitKwargsBase

#test
if __name__ == '__main__':
  class Parent(InitKwargs):
    """"""
    def __init__(self, **kwargs):
      """"""
      print kwargs

    
  class Child(Parent):
    """"""
    class InitKwargs:
      name = 'test'
  
  x = Child()
  #output:  {'name': 'test'}