def relpath(path, start=posixpath.curdir):
    """Return a relative version of a path"""
    if not path:
        raise ValueError("no path specified")

    start_list = posixpath.abspath(start).split(posixpath.sep)
    path_list = posixpath.abspath(path).split(posixpath.sep)

    # Work out how much of the filepath is shared by start and path.
    i = len(posixpath.commonprefix([start_list, path_list]))

    rel_list = [posixpath.pardir] * (len(start_list) - i) + path_list[i:]
    if not rel_list:
        return posixpath.curdir
    return posixpath.join(*rel_list)
Return a relative version of a path