How to sum a list in Python using for loop

First Declare a new variable with 0 and then iterate over the list by reassigning the variable to its value plus the current number to sum a list in Python using for loop.

Sum a list in python using for loop

Simple example code.

my_list = [2, 4, 6, 8]
sum = 0

for num in my_list:
    sum += num

print("Sum", sum)

Output:

This code achieves the same result:

• total += num
• total = total + num

Looping through a nested list and summing all elements of each internal list in Python

All_slips = [[1,2,3,4],[1,3,5,7],[1,2,7,9]]
summed_list = []
for sublist in All_slips:
    summed_list.append(sum(sublist))

That’s all. You can also employ a list comprehension.

summed_list = [sum(sublist) for sublist in All_slips]

Function for it

Encapsulate that for general use, e.g. in a function:

def sum_list(l):
    sum = 0
    for x in l:
        sum += x
    return sum

Now you can apply this to any list. Examples:

l = [1, 2, 3, 4, 5]
sum_list(l)

l = list(map(int, input("Enter numbers separated by spaces: ").split()))
sum_list(l)

Do comment if you have any doubts or suggestions on this Python list topic

Note: IDE: PyCharm 2021.3.3 (Community Edition)

Windows 10

Python 3.10.1

All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.