How to calculate a cumulative sum in Python
In this shot, we will learn how to calculate a cumulative sum in Python.
The cumulative sum is the sum of given numbers as it grows with the sequence. We will start by defining the problem statement, followed by an example.
Problem statement
Given a list of numbers, ln, calculate the cumulative sum for the list.
Example
Input:
ln = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Output: [1, 3, 6, 10, 15, 21, 28, 36, 45, 55]
Explanation
-
1 ===> 1
-
3 ===> 1 + 2
-
6 ===> 1 + 2 + 3
…
- 55 ===> 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10
Implementation
#given listln = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]#create empty cumulative listcl = []#declare variable for sums = 0#use for loop and append s to clfor i in ln:s += icl.append(s)#print cumulative listprint(cl)
Explanation
-
Line 2: We get the given list of numbers,
ln. -
Line 5: We declare an empty list
clto store the cumulative sum. -
Line 8: We declare and initialize variable
s, which keeps track of the sum of previous numbers. -
Line 11: We use a
forloop to traverse the given listln. -
Line 12: We add the present number
ito sums. -
Line 13: We append the sum
sto cumulative listcl. -
Line 16: We print
cl, which contains the cumulative sum for the given list of numbers.
