Pygame random spawning overlaps [duplicate]

I'm re-making the Chrome Dino Game in Pygame, and can't get the cactus to spawn randomly while never overlapping each other. I don't know what method / math equation to use and where, any idea ?

    def __init__(self) :
        self.type = random.randint(0, 2)
        self.image = SMALLCACTUSIMG[self.type]
        self.rect = self.image.get_rect()
        self.placer = random.randint(12, 20)
        self.rect.x = ((win_rect.width*self.placer) / 10)
        self.rect.y = 590

    def update(self):
        self.rect.x -= game_speed

        if self.rect.x < - self.rect.width :
            obstacles.remove(self)

    def draw(self):
        win.blit(self.image, (self.rect.x, self.rect.y))


class LargeCactus :
    # Same thing, except that the image isn't the same

def redraw():
    for obstacle in obstacles :
        obstacle.draw()
        obstacle.update()

    pygame.display.update()



while gamerunning:

    while len(obstacles) < 3 :

            if random.randint(0, 1) == 0 :
                cactus = SmallCactus()

            elif random.randint(0, 1) == 1 :
                cactus = LargeCactus()

            cactus.append(obstacles)