How do you find the sum of all even numbers in a list in python?

Using a generator expression:

>>> myList = [1, 3, 5, 6, 8, 10, 34, 2, 0, 3]
>>> sum(num for num in myList if not num%2)
60

Using filter():

>>> myList = [1, 3, 5, 6, 8, 10, 34, 2, 0, 3]
>>> sum(filter(lambda x: not x%2, myList))
60

Using a manual loop:

>>> myList = [1, 3, 5, 6, 8, 10, 34, 2, 0, 3]
>>> result = 0
>>> for item in myList:
...     if not item%2:
...             result += item
...
>>> result
60

The following article shows how given an integer list, we can produce the sum of all its odd and even digits.

Input : test_list = [345, 893, 1948, 34, 2346] 
Output : 
Odd digit sum : 36 
Even digit sum : 40 
Explanation : 3 + 5 + 9 + 3 + 1 + 9 + 3 + 3 = 36, odd summation.

Input : test_list = [345, 893] 
Output : 
Odd digit sum : 20 
Even digit sum : 12 
Explanation : 4 + 8 = 12, even summation. 

Method 1 : Using loop, str() and int()

In this, we first convert each element to string and then iterate for each of its element, and add to respective summation by conversion to integer.

Python3

test_list = [345, 893, 1948, 34, 2346]

print("The original list is : " + str(test_list))

odd_sum = 0

even_sum = 0

for sub in test_list:

    for ele in str(sub):

        if int(ele) % 2 == 0:

            even_sum += int(ele)

        else:

            odd_sum += int(ele)

print("Odd digit sum : " + str(odd_sum))

print("Even digit sum : " + str(even_sum))

Output

The original list is : [345, 893, 1948, 34, 2346]
Odd digit sum : 36
Even digit sum : 40

Method 2: Using loop and sum()

In this, we perform task of getting summation using sum(), and loop is used to perform the task of iterating through each element.

Python3

test_list = [345, 893, 1948, 34, 2346]

print("The original list is : " + str(test_list))

odd_sum = 0

even_sum = 0

for sub in test_list:

    odd_sum += sum([int(ele) for ele in str(sub) if int(ele) % 2 == 1])

    even_sum += sum([int(ele) for ele in str(sub) if int(ele) % 2 == 0])

print("Odd digit sum : " + str(odd_sum))

print("Even digit sum : " + str(even_sum))

Output

The original list is : [345, 893, 1948, 34, 2346]
Odd digit sum : 36
Even digit sum : 40

Method 3: Using list comprehension 

Python3

test_list = [345, 893, 1948, 34, 2346]

odd_sum = 0

even_sum = 0

odd_sum += sum([int(ele)

                for sub in test_list for ele in str(sub) if int(ele) % 2 == 1])

even_sum += sum([int(ele)

                 for sub in test_list for ele in str(sub) if int(ele) % 2 == 0])

print("Odd digit sum : " + str(odd_sum))

print("Even digit sum : " + str(even_sum))

Output

Odd digit sum : 36
Even digit sum : 40

Method 4: Using the enumerate function

Python3

test_list = [345, 893, 1948, 34, 2346]

odd_sum = 0

even_sum = 0

odd_sum += sum([int(ele) for i, sub in enumerate(test_list)

                for ele in str(sub) if int(ele) % 2 == 1])

even_sum += sum([int(ele) for i, sub in enumerate(test_list)

                 for ele in str(sub) if int(ele) % 2 == 0])

print("Odd digit sum : " + str(odd_sum))

print("Even digit sum : " + str(even_sum))

Output

Odd digit sum : 36
Even digit sum : 40

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