# Prefix sum array in Python using accumulate function

• Difficulty Level : Hard
• Last Updated : 28 Jul, 2022

We are given an array, find prefix sums of given array. Examples:

```Input : arr = [1, 2, 3]
Output : sum = [1, 3, 6]

Input : arr = [4, 6, 12]
Output : sum = [4, 10, 22]```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

A prefix sum is a sequence of partial sums of a given sequence. For example, the cumulative sums of the sequence {a, b, c, …} are a, a+b, a+b+c and so on. We can solve this problem in python quickly using accumulate(iterable) method.

Implementation:

## Python3

 `# function to find cumulative sum of array``from` `itertools ``import` `accumulate` `def` `cumulativeSum(``input``):``    ``print` `(``"Sum :"``, ``list``(accumulate(``input``)))` `# Driver program``if` `__name__ ``=``=` `"__main__"``:``    ``input` `=` `[``4``, ``6``, ``12``]``    ``cumulativeSum(``input``)`

Output

`Sum : [4, 10, 22]`
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