quote: http://stackoverflow.com/a/17601393/341744

http://i.stack.imgur.com/vrpFs.png

import pygame
import threading
import Queue

pygame.init()
screen = pygame.display.set_mode((300, 300))
quit_game = False

commands = Queue.Queue()

pos = 10, 10

m = {'w': (0, -10),
     'a': (-10, 0),
     's': (0, 10),
     'd': (10, 0)}

class Input(threading.Thread):
  def run(self):
    while not quit_game:
      command = raw_input()
      commands.put(command)

i = Input()
i.start()

old_pos = []

while not quit_game:
  try:
    command = commands.get(False)
  except Queue.Empty:
    command = None

  if command in m:
    old_pos.append(pos)
    pos = map(sum, zip(pos, m[command]))

  if pygame.event.get(pygame.QUIT):
    print "press enter to exit"
    quit_game = True

  pygame.event.poll()

  screen.fill((0, 0, 0))
  for p in old_pos:
      pygame.draw.circle(screen, (50, 0, 0), p, 10, 2)
  pygame.draw.circle(screen, (200, 0, 0), pos, 10, 2)
  pygame.display.flip()

i.join()