Class to avoid KeyError in str.format

import string


class BlankFormatter(string.Formatter):
    """ With the use of this class, we avoid the KeyError in dictionary based 
    str.format when the key is missing.
    """
    def __init__(self, default=''):
        self.default = default

    def get_value(self, key, args, kwargs):
        if isinstance(key, (str, unicode, )):
            return kwargs.get(key, self.default)
        return string.Formatter.get_value(key, *args, **kwargs)


kwargs = {"name": "mark", "adj": "mad"}     
fmt = BlankFormatter()
print fmt.format("My name is {name} and I'm really {adj}.", **kwargs)
# My name is mark and I'm really mad.
print fmt.format("My name is {name} and I'm really {adjective}.", **kwargs)
# My name is mark and I'm really .