lines_no_class.py

import pygame
import random

WIDTH, HEIGHT = 800, 600
NB_GROUPS, NB_LINES_PER_GROUP = 4, 6

vectors, lines = [], []

def next(l, v):
    for i in range(4):
        v[i] *= -1 if l[i] + v[i] not in range(WIDTH if i % 2 == 0 else HEIGHT) else 1
    return [l[i] + v[i] for i in range(4)]

for _ in range(NB_GROUPS):
    vectors.append([random.randint(-10, 10)]*4)
    lines.append([random.randrange(x) for x in [WIDTH, HEIGHT, WIDTH, HEIGHT]])
    
pygame.init()

screen = pygame.display.set_mode((WIDTH, HEIGHT))

while True:
    
    new_lines = [next(lines[g], vectors[g]) for g in range(NB_GROUPS)]
    
    lines = new_lines + lines[:(NB_LINES_PER_GROUP-1)*NB_GROUPS]

    screen.fill((0,0,0))
        
    for l in lines:
        pygame.draw.line(screen, (255,255,255), l[0:2], l[2:4])
    
    pygame.display.update()

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
    
    pygame.time.delay(100) # refresh ms