How to you find the cumulative sum in Python?

Let’s learn how to you find the cumulative sum in Python. We will use Numpy cumsum method for that.

To calculate cumulative sum in Python you need to use Numpy cumsum method. Your array is the parameter which needs to be used. I created sample 3 x 3 array which I will sum up cumulatively.

import numpy as np

my_array = np.array([0, 20, 25, 40, 100, 300,
                     500, 800, 2000]).reshape(3, -1)
print(f"This is my array: \n {my_array}")
my_cumsum_array = np.cumsum(my_array)
print(f"This is the cumulative sum of my array"
      f":\n {my_cumsum_array}")

As you can see Python summed every element up.

How to create a cumulative sum column in python?

It is also a possibility to calculate cumulative sum for columns. You need to add axis parameters to cumsum method.

import numpy as np

my_array = np.array([0, 20, 25, 40, 100, 300,
                     500, 800, 2000]).reshape(3, -1)
print(f"This is my array: \n {my_array}")
my_cumsum_array = np.cumsum(my_array, axis=0)
print(f"This is the cumulative columns sum of my array"
      f":\n {my_cumsum_array}")

Columns got sumed up.

How to create a cumulative sum row in python?

And now you can see the difference after changing axis value to 1. This is how to calculate cum sum for a row.

import numpy as np

my_array = np.array([0, 20, 25, 40, 100, 300,
                     500, 800, 2000]).reshape(3, -1)
print(f"This is my array: \n {my_array}")
my_cumsum_array = np.cumsum(my_array, axis=1)
print(f"This is the cumulative rows sum of my array"
      f":\n {my_cumsum_array}")

And this is how rows got summed up.