Python3列表索引错误

Question

Recently, I have started learning Python. I'd like to make a cosine distribution simulation. "Index Error:list index out of range" is shown on my display. but I think I define a length of list, and I write 0 < key < len(thickness). why the Error is shown on my display??

import math

def main():
    height = 20 
    thickness = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] 
    with open('output/output.csv', 'w', encoding = 'utf-8' ) as f:
        f.write('x,thikcness\n')
        for t in range(90):
            deg = t
            rad = math.radians(deg)
            x = height * math.tan(rad)
            key = round(x)

            if 0 < key <= len(thickness):
                thickness[key] += 1


        for t in len(thickness):
            f.write(str(thickness[t]) + '\n')

if __name__ == "__main__":
    main()

Answer 1

It should be if 0 <= key < len(thickness): . This is because array indices go from 0 to len(thickness)-1 , not 1 to len(thickness) .