not working

snakegame

import curses, math, signal, time,thread
#init
screen = curses.initscr()
#curses.noecho()
curses.curs_set(0)
curses.start_color();
curses.use_default_colors()
#colors


for i in range(0, curses.COLORS):
	curses.init_pair(i + 1,-1,i)
#ctrl-c handler
running=True
def signal_handler(signal, frame):
	global running
	running=False
signal.signal(signal.SIGINT, signal_handler)
#player
pos=[0,0]
direction=[0,-1]
parts=[]
screen.timeout(-1)
screen.nodelay(1)
#game loop
while running:
	#update
	dims=screen.getmaxyx()
	pos[0]+=direction[0]
	pos[1]+=direction[1]
	if pos[0]<0: pos[0]=dims[1]
	if pos[0]>dims[1]: pos[0]=0
	if pos[1]<0: pos[1]=dims[0]
	if pos[1]>dims[0]: pos[1]=0
	
	ch=screen.getch()
	if ch==ord('w'): direction=[0,-1]
	if ch==ord('s'): direction=[0,1]
	if ch==ord('a'): direction=[-1,0]
	if ch==ord('d'): direction=[1,0]
	#render
	screen.clear()
	screen.addstr(pos[1],pos[0],' ',curses.color_pair(4))
	screen.refresh()

	
curses.endwin()