Need help getting the line to & ldquo; draw & rdquo; in python (pygame)


ive been following a tutorial to learn pygame. the code below is to make a window (640 by 400) that s green. The program is also exposed to draw a red line across the screen. so far i have not been sucessfull in having the line appear. any suggestions?

#! /usr/bin/env python

import pygame

screen = pygame.display.set_mode((640, 400))
running = 1
green = 0, 255, 0
red = 255, 0, 0
point1 = 639, 479
point2 = 0, 0

while running:
    event = pygame.event.poll()
    if event.type == pygame.QUIT:
        running = 0

    pygame.draw.line(screen, red, point1, point2)

You need to call draw.line before the display.flip(), as it is now you are copying the data from the buffer to the display before the lines is drawn.