Pygame: Rescale pixel size

Question

With pygame, I created a 20x20 pixel window and added a 2x2 pixel rectangle. When I run the program, the window size is super small and I can barely see the rectangle. How can I increase the window size whilst keeping the number of pixels constant, i.e. increase the pixel size? I am aware of this similar question, but there a somewhat more complicated case is discussed.

import pygame
screen_width, screen_height = 20, 20
x, y = 10, 10
rect_width, rect_height = 2, 2
vel = 2
black = (0, 0, 0)
white = (255, 255, 255)
pygame.init()
win = pygame.display.set_mode((screen_width, screen_height))
run = True
while run:
    pygame.time.delay(100)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False
    win.fill(black)
    pygame.draw.rect(win, white, (x, y, rect_width, rect_height))
    pygame.display.update()
pygame.quit()

Answer 1

Don't draw directly to the screen, but to another Surface.

Then scale that new Surface to the size of the screen and blit it onto the real screen surface.

Here's an example:

import pygame
screen_width, screen_height = 20, 20

scaling_factor = 6

x, y = 10, 10
rect_width, rect_height = 2, 2
vel = 2
black = (0, 0, 0)
white = (255, 255, 255)
pygame.init()
win = pygame.display.set_mode((screen_width*scaling_factor, screen_height*scaling_factor))

screen = pygame.Surface((screen_width, screen_height))

run = True
while run:
    pygame.time.delay(100)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

    screen.fill(black)
    pygame.draw.rect(screen, white, (x, y, rect_width, rect_height))

    win.blit(pygame.transform.scale(screen, win.get_rect().size), (0, 0))
    pygame.display.update()
pygame.quit()