# Sum of NumPy Array in Python (3 Examples)

In this article, I’ll explain how to **apply the np.sum function** in Python.

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## Example Data & Libraries

We first have to load the NumPy library, to be able to use the functions that are contained in the library:

import numpy as np # Load NumPy library |

import numpy as np # Load NumPy library

Next, let’s also define some example data in Python:

my_array = np.array([[1, 2, 3], [4, 5, 6]]) # Create example array print(my_array) # Print example array # [[1 2 3] # [4 5 6]] |

my_array = np.array([[1, 2, 3], [4, 5, 6]]) # Create example array print(my_array) # Print example array # [[1 2 3] # [4 5 6]]

As you can see based on the previously shown output of the Python console, our example data is an array containing six values in three different columns.

## Example 1: Sum of All Values in NumPy Array

The following code demonstrates how to calculate the sum of all elements in a NumPy array.

For this task, we can apply the sum function of the NumPy library as shown below:

print(np.sum(my_array)) # Get sum of all array values # 21 |

print(np.sum(my_array)) # Get sum of all array values # 21

As shown by the previous output, the sum of all values in our array is 21.

## Example 2: Sum of Columns in NumPy Array

In Example 2, I’ll show how to find the sum of the values in a NumPy array column-wise.

To achieve this, we have to set the axis argument within the NumPy sum function to 0:

print(np.sum(my_array, axis = 0)) # Get sum of array columns # [5 7 9] |

print(np.sum(my_array, axis = 0)) # Get sum of array columns # [5 7 9]

## Example 3: Sum of Rows in NumPy Array

Similar to Example 2, we can also perform an addition of the values in a NumPy array by row.

For this, we have to specify the axis argument to be equal to 1:

print(np.sum(my_array, axis = 1)) # Get sum of array rows # [ 6 15] |

print(np.sum(my_array, axis = 1)) # Get sum of array rows # [ 6 15]

## Video, Further Resources & Summary

Have a look at the following video on my YouTube channel. I illustrate the Python programming codes of this post in the video.

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Furthermore, you could have a look at some of the other tutorials on this website:

- Calculate Sum in Python
- Find Sum by Group in Python
- Convert pandas DataFrame Index to List & NumPy Array in Python
- Get Median of Array with np.median Function of NumPy Library in Python
- Convert pandas DataFrame to NumPy Array in Python
- The Python Programming Language

At this point you should know how to **use the np.sum function to get the sum of an array** in the Python programming language. Let me know in the comments section below, if you have further questions.