Subclass dictionaries with validation. A fun pattern for wrapping JSON APIs!

DictFactory.py

def DictFactory(name, argnames, default_keys={}):
    def __init__(self, **kwargs):
        for key, value in kwargs.items():
            if key not in argnames:
                raise TypeError("Argument %s not valid for %s" 
                    % (key, self.__class__.__name__))
        kwargs.update(default_keys)
        dict.__init__(self, **kwargs)

    newclass = type(name, (dict,),{"__init__": __init__})
    
    return newclass