def get_nbr_vertices(path_sfm):
    """ Read sf_data_file and get number of vertices.
        Return: nbr of vertices."""
    pipe = open(path_sfm, 'r')
    sfm_data = pipe.read()
    target = 'element vertex '
    n: int = int([el for el in sfm_data.split('\n') if el.startswith(target)][0].split(target)[1])
    return n