Why won't my pygame images load - python-2.7

Question

I'm relatively new to python and pygame, so this is most certainly just my own inexperience. However, in my game loop, every time an image or shape is blitted to the screen, it doesn't disappear until another image or shape is blitzed over it.
game_loop function
def game_loop():
road
carImg
pygame.init()
pygame.mixer.init()
pygame.mixer.music.load('Rally-X.mp3')
pygame.mixer.music.play()
x = (display_width * 0.45)
y = (display_height * 0.8)
x_change = 0
road_starty = -23
road_speed = 4
thing_starty = -600
thing_speed = 4
thing_width = 100
thing_height = 100
thing_startx = random.randrange(0, display_width)
carImgCount = 1
dodged = 0
gameExit = False
pygame.display.update()
while not gameExit:
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
quit()
pygame.display.update()
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_LEFT or event.key == pygame.K_a:
x_change = -5
if event.key == pygame.K_RIGHT or event.key == pygame.K_d:
x_change = 5
if event.key == pygame.K_p:
paused()
pygame.display.update()
if event.type == pygame.KEYUP:
if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT or event.key == pygame.K_d or event.key == pygame.K_a:
x_change = 0
pygame.display.update()
x += x_change
gameDisplay.blit(road,(0,road_starty))
car(x,y)
#things(thingx, thingy, thingw, thingh, color)
things(thing_startx, thing_starty, thing_width, thing_height)
road_starty += road_speed
thing_starty += thing_speed
things_dodged(dodged)
if x > display_width - car_width or x < 0:
crash()
if thing_starty > display_height:
thing_starty = 0 - thing_height
thing_startx = random.randrange(0,display_width)
dodged += 1
if thing_speed <= 10:
thing_speed += 1
pygame.display.update()
if y < thing_starty+thing_height:
#print('y crossover')
if x > thing_startx and x < thing_startx + thing_width or x+car_width > thing_startx and x + car_width < thing_startx+thing_width:
#print('x crossover')
crash()
pygame.display.update()
if road_starty == 0:
road_starty = -23
if dodged > 9:
things(thing_startx, thing_starty, thing_width, thing_height)
pygame.display.update()
clock.tick(60)
I started just calling the pygame.display.update() function just about everywhere in the game_loop function to try and fix it, but it still doesn't seem to help.
Here is a picture of the code acting up in action:
Those red lines are supposed to be squares, and the car... isn't supposed to look like that. If someone could tell me what I'm doing wrong, that'd be awesome.

Answer 1

You have to clear screen before you draw new frame.
gameDisplay.fill((0,0,0))
And after clearing screen you have to draw all elements again.
You will have to reorganize you code to fill, draw and update in one place
You can organize mainloop this way (simple example)
# --- mainloop ---
clock = pygame.time.Clock()
is_running = True
while is_running:
# --- events ---
for event in pygame.event.get():
# --- global events ---
if event.type == pygame.QUIT:
is_running = False
elif event.type == pygame.KEYDOWN:
if event.key == pygame.K_ESCAPE:
is_running = False
# --- objects events (without draws)---
'''
player.handle_event(event)
'''
# --- updates (without draws)---
'''
player.update()
'''
# --- draws (without updates) ---
screen.fill(BLACK) # only once in loop
'''
player.draw(screen)
'''
pygame.display.update() # only once in loop
# --- FPS ---
clock.tick(25)
full example: PyGame simple template and other templates

Answer 2

there is an easy, cheap way of getting the image off the screen...
say the screen is 400 x 400 just change the coordinates of the picture to where the x is like 500 and the y is like 600 so that it is placed outside of the pygame canvas