def scalexy(sizex=1, sizey=1):
    """scalexy(sizex=1, sizey=1) -> stereo

    Return a two-dimensional stereo scaling. If sizey is 1 (or omitted),
    this is equivalent to scale(sizex).
    """
    if sizex == 1 and sizey == 1:
        return ()
    if sizey == 1:
        return float(sizex), 0.0
    return float(sizex), 0.0, float(sizey), 0.0
