Find sum of elements in List Python (original) (raw)
Last Updated : 05 May, 2025
Finding the **sum of elements in a **list means adding all the values together to get a single total. **For example, given a **list like [10, 20, 30, 40, 50], you might want to calculate the total sum, which is 150. Let’s explore these different methods to do this efficiently.
Using sum()
**sum() function is the most efficient way to calculate the sum of all elements in a list. It automatically takes care of iterating over the list and summing up the values for you.
Python `
a = [10, 20, 30, 40, 50] res = sum(a) print(res)
`
**Explanation: sum() function adds all the numbers in the list **a and stores the result in **res.
Using for loop
**For loop gives you more control over the process. By manually iterating over the list, you can accumulate the sum step by step.
Python `
a = [10, 20, 30, 40, 50] res = 0 # Initialize sum variable
for i in a: res += i print(res)
`
**Explanation: For loop iterates through each element in the list, adding it to **res in each step until all elements are summed.
Using list comprehension
**List comprehension allows you to create a new list based on an existing one and then use **sum() to calculate the total. This is a more Pythonic way to do things when you want to transform the list first.
Python `
a = [10, 20, 30, 40, 50]
res = sum([i for i in a]) print(res)
`
**Explanation: List comprehension creates a new list identical to **a and the **sum() function then calculates the total of its elements, storing the result in res.
Using reduce()
**reduce() function from the functools module applies a function (in this case, addition) to the elements of the list cumulatively. This method is less commonly used but provides a functional programming style solution.
Python `
from functools import reduce a = [10, 20, 30, 40, 50]
res = reduce(lambda x, y: x + y, a) print(res)
`
**Explanation: reduce() function uses the **lambda to cumulatively add pairs of elements from left to right, resulting in the total sum stored in **res.