How to draw a dashed line in python using pygame?

Question

I am creating a pong game in python using pygame, and I wish to draw a dashed line down the middle. I think I have the correct code to draw the dashed line but it will not work.

   for i in range(0, HEIGHT, HEIGHT//20):
        if i % 2 == 1:
            continue
        pygame.draw.rect(win, WHITE, (WIDTH//2 - 5, i, 10, HEIGHT//20))

I tried this and expected it to draw a dashed line but it didn't. Here is my whole code:

import pygame
pygame.init()

WIDTH, HEIGHT = 1200, 800
NAME = "Pong"
WIN = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption(NAME)

WHITE = (255,255,255)
BLACK = (0,0,0)

PADDLE_WIDTH, PADDLE_HEIGHT = 10, 200

FPS = 60

class Paddle:
    COLOUR = WHITE
    VEL = 5

    def __init__(self, x, y, width, height):
        self.x = x
        self.y = y
        self.width = width
        self.height = height

    def draw(self, win):
        pygame.draw.rect(win, self.COLOUR, (self.x, self.y, self.width, self.height))

    def move(self, up):
        if up:
            self.y -= self.VEL
        else:
            self.y += self.VEL


def draw(win, paddles):
    win.fill(BLACK)
    for paddle in paddles:
        paddle.draw(win)

    for i in range(0, HEIGHT, HEIGHT//20):
        if i % 2 == 1:
            continue
        pygame.draw.rect(win, WHITE, (WIDTH//2 - 5, i, 10, HEIGHT//20))


    pygame.display.update()

def handle_paddle_movement(keys, left_paddle, right_paddle):
    if keys[pygame.K_w] and left_paddle.y - left_paddle.VEL > 0:
        left_paddle.move(True)
    if keys[pygame.K_s] and left_paddle.y + left_paddle.VEL + left_paddle.height < HEIGHT:
        left_paddle.move(False)
    if keys[pygame.K_UP] and right_paddle.y - right_paddle.VEL > 0:
        right_paddle.move(True)
    if keys[pygame.K_DOWN] and right_paddle.y + right_paddle.VEL + right_paddle.height < HEIGHT:
        right_paddle.move(False)

def main():
    run = True
    clock = pygame.time.Clock()

    left_paddle = Paddle(PADDLE_WIDTH, HEIGHT//2 - PADDLE_HEIGHT//2, PADDLE_WIDTH, PADDLE_HEIGHT)
    right_paddle = Paddle(WIDTH - PADDLE_WIDTH*2, HEIGHT//2 - PADDLE_HEIGHT//2, PADDLE_WIDTH, PADDLE_HEIGHT)

    while run:
        clock.tick(FPS)
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                run = False
                break 

        keys = pygame.key.get_pressed()
        handle_paddle_movement(keys, left_paddle, right_paddle)

        draw(WIN, [left_paddle, right_paddle])
    pygame.quit()


if __name__ == '__main__':
    main()

Answer 1

This is the rectangle you are drawing each loop:

#    x         y  width  height
(WIDTH//2 - 5, i, 10, HEIGHT//20)

You should replace the HEIGHT//20 with a smaller value so each rect isn't so tall. Try something like this instead:

pygame.draw.rect(win, WHITE, (WIDTH//2 - 5, i, 10, 20))

Answer 2

In your loop iterates with a step of HEIGHT//20 . There for i is always divisible by 2 with out a rest. There are many options to solve your problem. eg:

Option 1 use enumerate :

for i, y in enumerate(range(0, HEIGHT, HEIGHT//20)):
    if i % 2 == 1:
        continue
    pygame.draw.rect(win, WHITE, (WIDTH//2 - 5, y, 10, HEIGHT//20))

Option 2 iterate with a step of HEIGHT//10 :

for y in range(0, HEIGHT, HEIGHT//10):
    pygame.draw.rect(win, WHITE, (WIDTH//2 - 5, y, 10, HEIGHT//20))