[pygame] possible to get rid of ghost image after rotating a line?

[tom arnall]

I want to rotate a line around a point. The code that follows does
this, BUT when it draws a line, it leaves next to the line its ghost.
Is this a problem with pygame, or is there a change I can make in the
code which will make the problem go away?


import pygame, sys
from pygame.locals import *
import time

pygame.init()

#create a surface that will be seen by the user
screen =  pygame.display.set_mode((400, 400))

#create a varible for degrees pf rotation
degree = 0
while True:

    for event in pygame.event.get():
        # quit the game if escape is pressed
        if event.type == QUIT:
            sys.exit()
        elif event.type == KEYDOWN and\
                event.key == K_ESCAPE:
            sys.exit()

    #clear screen at the start of every frame
    screen.fill((40, 40, 40))

    #create new surface with white BG
    surf =  pygame.Surface((1000, 5))
    surf.fill((255, 255, 255))
    #set a color key for blitting
    surf.set_colorkey((255, 0, 0))


    ##ORIGINAL UNCHANGED
    #where will the static image be placed:
    where = (0,200)

    #draw surf to screen and catch the rect that blit returns
    blittedRect = screen.blit(surf, where)

    ##ROTATED
    #get center of surf for later
    oldCenter = blittedRect.center

    #rotate surf by DEGREE amount degrees
    rotatedSurf =  pygame.transform.rotate(surf, degree)

    #get the rect of the rotated surf and set it's center to the oldCenter
    rotRect = rotatedSurf.get_rect()
    rotRect.center = oldCenter

    #draw rotatedSurf with the corrected rect so it gets put in the proper spot
    screen.blit(rotatedSurf, rotRect)

    #change the degree of rotation
    degree += 5
    if degree > 360:
        degree = 0

    #show the screen surface
    pygame.display.flip()

    #wait 60 ms until loop restart
    pygame.time.wait(60)