Python – Summation of Unique elements

This article focuses on one of the operation of getting the unique list from a list that contains a possible duplicates and performing its summation. This operations has large no. of applications and hence it’s knowledge is good to have. 

Method 1 : Naive method + sum() In naive method, we simply traverse the list and append the first occurrence of the element in new list and ignore all the other occurrences of that particular element. The task of summation is performed using sum(). 

Python3

# Python 3 code to demonstrate
# Summation of Unique elements
# using naive methods + sum()

# initializing list
test_list = [1, 3, 5, 6, 3, 5, 6, 1]
print ("The original list is : " + str(test_list))

# using naive method + sum()
# Summation of Unique elements
# from list
res = []
for i in test_list:
    if i not in res:
        res.append(i)
res = sum(res)

# printing list after removal
print ("The unique elements summation : " + str(res))

Output

The original list is : [1, 3, 5, 6, 3, 5, 6, 1]
The unique elements summation : 15

Time Complexity: O(n), where n is the number of elements in the list “test_list”.
Auxiliary Space: O(n), where n is the number of elements in the list “test_list”.

Method 2 : Using set() + sum() This is the most popular way by which the duplicated are removed from the list. After that the summation of list can be performed using sum(). 

Python3

# Python 3 code to demonstrate
# Summation of Unique elements
# using set() + sum()

# initializing list
test_list = [1, 5, 3, 6, 3, 5, 6, 1]
print ("The original list is : " + str(test_list))

# using set() + sum()
# Summation of Unique elements
# from list
res = sum(list(set(test_list)))

# Summation of Unique elements
# using set() + sum()
print ("The unique elements summation : " + str(res))

Output

The original list is : [1, 5, 3, 6, 3, 5, 6, 1]
The unique elements summation : 15

Method #3:Using Counter() function

Python3

# Python 3 code to demonstrate
# Summation of Unique elements
from collections import Counter
# initializing list
test_list = [1, 5, 3, 6, 3, 5, 6, 1]
print("The original list is : " + str(test_list))

freq = Counter(test_list)
res = sum(freq.keys())

# Summation of Unique elements
print("The unique elements summation : " + str(res))

Output

The original list is : [1, 5, 3, 6, 3, 5, 6, 1]
The unique elements summation : 15

Time Complexity: O(N)
Auxiliary Space: O(N)

Method #4:Using Operator.countOf() method

Python3

# Python 3 code to demonstrate
# Summation of Unique elements
import operator as op
# initializing list
test_list = [1, 3, 5, 6, 3, 5, 6, 1]
print ("The original list is : " + str(test_list))

# using naive method + sum()
# Summation of Unique elements
# from list
res = []
for i in test_list:
    if op.countOf(res,i)==0:
        res.append(i)
res = sum(res)

# printing list after removal
print ("The unique elements summation : " + str(res))

Output

The original list is : [1, 3, 5, 6, 3, 5, 6, 1]
The unique elements summation : 15

Time Complexity:O(N)
Auxiliary Space:O(N)

Method #5:Using numpy method

Python3

#Python 3 code to demonstrate
#Summation of Unique elements
#using numpy
import numpy as np

#initializing list
test_list = [1, 3, 5, 6, 3, 5, 6, 1]
print ("The original list is : " + str(test_list))

#using numpy
#Summation of Unique elements
#from list
res = np.sum(np.unique(test_list))

#printing result
print ("The unique elements summation : " + str(res))
#This code is contributed by Edula Vinay Kumar Reddy

Output:
The original list is : [1, 3, 5, 6, 3, 5, 6, 1]
The unique elements summation : 15

Time Complexity:O(N)
Auxiliary Space:O(N)

Method #6:Using List Comprehension:

Python3

test_list = [1, 3, 5, 6, 3, 5, 6, 1]
print("The original list is : ", test_list)
res = sum([i for i in set(test_list) if i <= 6])
print("The unique elements summation : ", res)
#This code is contributed by Jyothi pinjala.

Output

The original list is :  [1, 3, 5, 6, 3, 5, 6, 1]
The unique elements summation :  15

Time Complexity:O(N)
Auxiliary Space:O(N)