def _write_a_tikz_coordinate(name, xy, num_fmt):
    """Write a TikZ coordinate definition.

    Parameters
    ----------
    name : str
        TikZ coordinate identified / name.
    xy : list or tuple of floats
        (x, y)-coordinates.
    num_fmt : str
        Specification of the numbers format, e.g. '.4f'.


    Returns
    -------
    str
        TikZ coordinate definition without newline char.

    """
    fmt_str = "{:" + num_fmt + "}"

    tex_str = "\\coordinate ({:s})".format(name)
    tex_str += " at ("
    tex_str += ", ".join(map(fmt_str.format, xy))
    tex_str += ");"

    return tex_str