sumRange.py

# from https://leetcode.com/problems/range-sum-query-immutable/
class NumArray(object):
    def __init__(self, nums):
        self.sums = []
        sum = 0
        for num in nums:
            sum += num
            self.sums.append(sum)
        

    def sumRange(self, i, j):
        return self.sums[j] if i == 0 else self.sums[j] - self.sums[i - 1]

# Your NumArray object will be instantiated and called as such:
# numArray = NumArray(nums)
# numArray.sumRange(0, 1)
# numArray.sumRange(1, 2)