import pygame, random
pygame.init()
# Определить некоторые цвета
black    = (0,0,0)
white    = (255,255,255)
green    = (0,255,0)
red      = (255,0,0)
blue     = (0,0,255)
size=[700,500]
screen=pygame.display.set_mode(size)
pygame.display.set_caption("Obychenie")
screen.fill(white)# Очистить экран и установить фон
done = False
last_pos = (0, 0)
color = (black)# цвет отпечатка мыши
radius = 2
def roundline(srf, color, start, end, radius):
    dx = end[0]-start[0]
    dy = end[1]-start[1]
    distance = max(abs(dx), abs(dy))
    for i in range(distance):
        x = int( start[0]+float(i)/distance*dx)
        y = int( start[1]+float(i)/distance*dy)
        pygame.draw.circle(srf, color, (x, y), radius)
try:
    while True:
        e = pygame.event.wait()
        if e.type == pygame.QUIT:
            raise StopIteration
        if e.type == pygame.MOUSEBUTTONDOWN:
            pygame.draw.circle(screen, color, e.pos, radius)
            done = True
        if e.type == pygame.MOUSEBUTTONUP:
            done = False
        if e.type == pygame.MOUSEMOTION:
            if done:
                pygame.draw.circle(screen, color, e.pos, radius)
                roundline(screen, color, e.pos, last_pos,  radius)
            last_pos = e.pos
        for y_offset in range(10,280,20):  
            pygame.draw.line(screen,green,[280,10+y_offset],[420,20+y_offset],2)
        for y_offset in range(20,280,20):
            pygame.draw.line(screen,green,[280,20+y_offset],[420,10+y_offset],2)
               pygame.draw.rect(screen,black,[50,20,250,280],2)
        pygame.draw.rect(screen,black,[400,20,250,280],2)  
        pygame.draw.rect(screen,blue,[280,20,40,280],1)  
        pygame.draw.rect(screen,blue,[380,20,40,280],1)
        pygame.display.flip()
except StopIteration:
    pass
pygame.quit()