opengl - pyglet on_key_press Error: 'key' not defined -

i'm using pyglet , trying handle keypress events on_key_press method. keep getting same error when defining events specific symbols key.up:

nameerror: global name 'key' not defined  

based on examples i've seen in pyglet documentation, no prior definition of key necessary. mistaken or there else i'm missing?

here's code i'm using event handler

@window.event def on_key_press(symbol, modifier):     if symbol == key.up:         data.rx -= 2         draw()     elif symbol == key.down:         data.rx += 2         draw()     elif symbol == key.space:         close()