Python code to find sum of elements in given array

#!/usr/bin/python
# -*- coding: utf-8 -*-
# Python 3 code to find sum
# of elements in given array

def _sum(arr):
   # initialize a variable
   # to store the sum
   # while iterating through
   # the array later
   sum = 0
   # iterate through the array
   # and add each element to the sum variable
   # one at a time
   for i in arr:
       sum = sum + i
   return sum

# driver function
arr = []
# input values to list
arr = [12, 3, 4, 15]
# calculating length of array
n = len(arr)
ans = _sum(arr)
# display sum
print ('Sum of the array is ', ans)