<h2>In Pygame 2</h2>

In pygame 2 the display surface is automatically resized when the window is - set_mode() should not be called. The VIDEORESIZE event instead lets us handle any other surfaces, or anything else, we might want to resize.  
<br><br>
<b>Example:</b><br>
<code>
import pygame
from pygame.locals import *
pygame.init()
screen = pygame.display.set_mode((500, 500), RESIZABLE)
pic = pygame.image.load("example.png")  # You need an example picture in the same folder as this file!
running = True
while running:
    pygame.event.pump()
    event = pygame.event.wait()
    if event.type == QUIT:
        running = False
    elif event.type == VIDEORESIZE:
        screen.blit(pygame.transform.scale(pic, event.dict['size']), (0, 0))
        pygame.display.update()
    elif event.type == VIDEOEXPOSE:  # handles window minimising/maximising
        screen.fill((0, 0, 0))
        screen.blit(pygame.transform.scale(pic, screen.get_size()), (0, 0))
        pygame.display.update()  

</code>
<br><br>
<h2>In Pygame 1</h2>
<br><br>
<b>Example:</b><br>
<code>
import pygame
from pygame.locals import *
pygame.init()
screen=pygame.display.set_mode((500,500),HWSURFACE|DOUBLEBUF|RESIZABLE)
pic=pygame.image.load("example.png") #You need an example picture in the same folder as this file!
screen.blit(pygame.transform.scale(pic,(500,500)),(0,0))
pygame.display.flip()
while True:
    pygame.event.pump()
    event=pygame.event.wait()
    if event.type==QUIT: pygame.display.quit()
    elif event.type==VIDEORESIZE:
        screen=pygame.display.set_mode(event.dict['size'],HWSURFACE|DOUBLEBUF|RESIZABLE)
        screen.blit(pygame.transform.scale(pic,event.dict['size']),(0,0))
        pygame.display.flip()
</code>