Trusted answers to developer questions
Trusted Answers to Developer Questions

Related Tags

numpy
python
communitycreator
diagonal

# What is the numpy.diagonal() function from NumPy in Python? Onyejiaku Theophilus Chidalu

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

### Overview

The diagonal() function in Python is simply used to return a specified diagonal from a given 2D array.

### Syntax

numpy.diagonal(a, offset=0, axis1=0, axis2=1)


Note: To use numpy.diagonal() function, first import numpy.

### Parameter value

The diagonal() function takes the following parameter values:

• a: This represents the array_like object from which the diagonal is taken.
• offset: This represents the offset to the diagonal from the main diagonal. It could take a negative or positive integer value. The default to the main diagonal is 0. This is optional.
• axis1: This represents the axis to be used as the first axis of the 2D sub-arrays from which the diagonals should be taken. The default value is 0.
• axis2: This represents the axis to be used as the second axis of the 2D sub-arrays from which the diagonals should be taken. The default value is 1.

### Return value

The diagonal() function returns a diagonal array.

### Code example

import numpy as np# creating an arraymyarray = np.arange(9).reshape(3, 3)# implementing the diagonal() function diagarray = np.diagonal(myarray, 0, 0, 1)print(myarray)print(diagarray)
Implementing the diagonal() function

### Explanation

• Line 1: We import the numpy library.
• Line 4: We create a 2D array myarray of 9 elements with a dimension of 3 by 3, that is 3 rows and 3 columns, using the arange() function.
• Line 7: We implement the diag() function on the array myarray using the main diagonal k = 0, default axis1, 0, and a default axis2, 0. The result is assigned to a new variable diagarray.
• Line 9: We print the array myarray.
• Line 10: We print the new diagonal array diagarray.

RELATED TAGS

numpy
python
communitycreator
diagonal

CONTRIBUTOR Onyejiaku Theophilus Chidalu

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

Keep Exploring

Learn in-demand tech skills in half the time 