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Decorator for defining functions with keyword-only arguments (Python recipe) by Oscar Byrne
ActiveState Code (http://code.activestate.com/recipes/579079/)

Python2.x implementation of python3's keyword-only arguments (aka arguments that must be specified as keywords, and are not automatically filled in by positional arguments - see PEP 3102).

Python, 26 lines
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from functools import wraps


class default_kwargs(object):
    """
    Metadecorator for ensuring specified keys are present in kwargs before calling function

    Will only use default value if the key is not already present in kwargs.
    """
    def __init__(self, **kwargs):
        self.defaults = kwargs
    def __call__(self, wrapped):
        @wraps(wrapped)
        def wrapper(*args, **kwargs):
            new_kwargs = self.defaults.copy()
            new_kwargs.update(kwargs)
            return wrapped(*args, **new_kwargs)
        return wrapper


## Usage example:

@default_kwargs(echo=True)
def f(*args, **kwargs):
  if kwargs["echo"]:
    print args, kwargs
Tags: arguments, decorator, decorators, keyword, metadecorator, positional, python2, python3