Bollinger Band Position

Problem

Compute where the last price sits inside a Bollinger band built from the last k prices: position = (last - lower) / (upper - lower), with bands mean ± num_std * population standard deviation.

Return 0.5 when the standard deviation is zero, and None if k is not positive or exceeds the series length.

Hint

A value of 1.0 means the price sits exactly on the upper band.

Test cases

case 1

in: [[1,2,3,4,5],5,2]

expected: 0.8535533905932738

case 2

in: [[5,5,5],3,2]

expected: 0.5

case 3

in: [[1,2,3],0,2]

expected: null

case 4

in: [[1,2,3],5,2]

expected: null

Starter codePython

def bollinger_position(prices, k, num_std):
    # Your code here
    pass

4 test cases · run your code against them in the editor