def zpad(keys, values, default=None):
    """zips two lits and pads the second to match the first in length"""
    keys_len = len(keys)
    values_len = len(values)
    if keys_len < values_len:
        raise ValueError('keys must be as long or longer than values')
    values += [default] * (keys_len - values_len)
    return zip(keys, values)
