def listify(x, none_value=[]):
    """Make a list of the argument if it is not a list."""

    if isinstance(x, list):
        return x
    elif isinstance(x, tuple):
        return list(x)
    elif x is None:
        return none_value
    else:
        return [x]
def listify ( x , none_value = [ ] ) : if isinstance ( x , list ) : return x elif isinstance ( x , tuple ) : return list ( x ) elif x is None : return none_value else : return [ x ]
Make a list of the argument if it is not a list.