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Python Program to Find Sum of Array

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Given an array of integers, find the sum of its elements.

Examples:

Input : arr[] = {1, 2, 3}
Output : 6
Explanation: 1 + 2 + 3 = 6

This Python program calculates the sum of an array by iterating through each element and adding it to a running total. The sum is then returned. An example usage is provided to demonstrate the calculation of the sum for a given array.

Python Program to Find Sum of Array

Iterating through the array and adding each element to the sum variable and finally displaying the sum.

Python3

# 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)
 
 
# main function
if __name__ == "__main__":
    # input values to list
    arr = [12, 3, 4, 15]
 
    # calculating length of array
    n = len(arr)
    # calling function ans store the sum in ans
    ans = _sum(arr)
    # display sum
    print('Sum of the array is ', ans)

                    

Output
Sum of the array is  34

Time complexity: O(n), 
Auxiliary Space: O(1)

Python Program to Find Sum of Array Using sum()

Using the built-in function sum(). Python provides an inbuilt function sum() which sums up the numbers in the list. 

Python3

# Python 3 code to find sum
# of elements in given array
 
# input values to list
arr = [12, 3, 4, 15]
 
# sum() is an inbuilt function in python that adds
# all the elements in list,set and tuples and returns
# the value
ans = sum(arr)
 
# display sum
print('Sum of the array is ', ans)

                    

Output
Sum of the array is  34

Time complexity: O(n) 
Auxiliary Space: O(1)

Python Program to Find Sum of Array Using reduce method

Using the reduce method. Array.reduce() method is used to iterate over the array and get the summarized result from all elements of array.

Python

from functools import reduce
# Python 3 code to find sum
# of elements in given array
 
 
def _sum(arr):
 
    # iterate over array
    # using reduce and get
    # sum on accumulator
    sum = reduce(lambda a, b: a+b, arr)
 
    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)

                    

Output
('Sum of the array is ', 34)

Time complexity : O(n)
Auxiliary Space : O(1)

Python Program to Find Sum of Array Using enumerate function 

This code calculates the sum of elements in the list list1 using a loop. It iterates through each element, adds it to the running sum s, and then prints the final sum.

Python3

list1 = [12, 3, 4, 15];s=0
for i,a in enumerate(list1):
  s+=a
print(s)

                    

Output
34

Time complexity: O(n)
Auxiliary Space: O(1)

Python Program to Find Sum of Array Using Divide and conquer

Define a function that takes an array and two indices low and high. If low == high, return the element at that index. Calculate the midpoint of the array as mid = (low + high) // 2.Recursively find the sum of the left subarray as left_sum = sum_of_array(arr, low, mid). Recursively find the sum of the right subarray as right_sum = sum_of_array(arr, mid+1, high). Return the sum of the left and right subarrays as left_sum + right_sum.

Python3

def sum_of_array(arr, low, high):
    if low == high:
        return arr[low]
    mid = (low + high) // 2
    left_sum = sum_of_array(arr, low, mid)
    right_sum = sum_of_array(arr, mid+1, high)
    return left_sum + right_sum
#Examples
arr = [1, 2, 3]
print(sum_of_array(arr, 0, len(arr)-1)) # Output: 6
 
arr = [15, 12, 13, 10]
print(sum_of_array(arr, 0, len(arr)-1)) # Output: 50

                    

Output
6
50

Please refer complete article on Program to find sum of elements in a given array for more details!

Python Program to Find Sum of Array Using counter method.

This program finds the sum of an array using the Counter class from the collections module in Python. The Counter class is used to count the occurrences of elements in the input array. The program then iterates over the items in the counter and calculates the sum of the array.

Python3

from collections import Counter
 
arr = [12, 3, 4, 15]
c = Counter(arr)
sum = 0
 
for key, value in c.items():
    sum += key * value
 
print("Sum of the array is", sum)

                    

Output
Sum of the array is 34


Last Updated : 03 Jul, 2023
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