def do_format(value, *args, **kwargs):
    """
    Apply python string formatting on an object:

    .. sourcecode:: jinja

        {{ "%s - %s"|format("Hello?", "Foo!") }}
            -> Hello? - Foo!
    """
    if args and kwargs:
        raise FilterArgumentError('can\'t handle positional and keyword '
                                  'arguments at the same time')
    return soft_unicode(value) % (kwargs or args)