scope of variables

[Christoph Lehmann]

please, don't laugh at me, but I am new to pyhton

why are the variables last_image not seen within the scope of the
function, or: how to make them seen (global)

image_time = []
last_image = -1
def image_selector( t ):
    i = int(t/duration_per_image)
    if i <> last_image:
        image_time.append[VisionEgg.timing_func()]
    last_image = i
    return [ preloaded_stimulus_list[i] ]


thanks
chris
-- 
Christoph Lehmann 
Department of Psychiatric Neurophysiology 
University Hospital of Clinical Psychiatry 
Waldau 
CH-3000 Bern 60 
Switzerland 

Phone:  ++41 31 930 93 83 
Fax:    ++41 31 930 96 61 
Email:  lehmann at puk.unibe.ch 
Web: