# Alternate element summation in list (Python)

PythonServer Side ProgrammingProgramming

Given a list of numbers in this article we are going to calculate the sum of alternate elements in that list.

## With list slicing and range

Every second number and also use the range function along with length function to get the number of elements to be summed.

## Example

Live Demo

listA = [13,65,78,13,12,13,65]
# printing original list
print("Given list : " , str(listA))
# With list slicing
res = [sum(listA[i:: 2])
for i in range(len(listA) // (len(listA) // 2))]
# print result
print("Sum of alternate elements in the list :\n ",res)

## Output

Running the above code gives us the following result −

Given list : [13, 65, 78, 13, 12, 13, 65]
Sum of alternate elements in the list :
[168, 91]

## With range and %

Use the percentage operator to separate the numbers at Even and Odd positions. And then add the elements to the respective position of a new empty list. Finally giving a list which shows sum of elements at odd position and sum of elements at even position.

## Example

Live Demo

listA = [13,65,78,13,12,13,65]
# printing original list
print("Given list : " , str(listA))
res = [0, 0]
for i in range(0, len(listA)):
if(i % 2):
res += listA[i]
else :
res += listA[i]
# print result
print("Sum of alternate elements in the list :\n ",res)

## Output

Running the above code gives us the following result −

Given list : [13, 65, 78, 13, 12, 13, 65]
Sum of alternate elements in the list :
[168, 91]