How to make a 2d NumPy array a 3d array?

Learn, how to make a 2d NumPy array a 3d array in Python? By Pranit Sharma Last updated : December 23, 2023

NumPy is an abbreviated form of Numerical Python. It is used for different types of scientific operations in python. Numpy is a vast library in python which is used for almost every kind of scientific or mathematical operation. It is itself an array which is a collection of various methods and functions for processing the arrays.

Problem statement

Suppose that we are given a 2d array with shape (x, y) which we want to convert to a 3d array with shape (x, y, 1).

Making a 2d NumPy array a 3d array

When we convert a 2d array into a 3d array, we are just adding one more axis or we are just modifying the shape of the array.

To make a 2d NumPy array a 3d array, we always use numpy.newaxis to add a new axis or to increase the dimension of the numpy array. If we are given a numpy array of shape (x,y), np.newaxis will add 1 more axis and the shape will become (x,y,1).

Note

Use ndarray.shape to get the shape. The ndarray.shape returns a tuple of array dimensions.

Let us understand with the help of an example,

Python program to make a 2d NumPy array a 3d array

# Import numpy
import numpy as np

# Creating a numpy array
arr = np.array([[1,2],[3,4]])

# Display original array
print("Original Array:\n",arr,"\n")

# Display current shape
print("Current shape:\n",arr.shape)

# Adding a new axis and making 
# the array as a 3d array
res = arr[:, :, np.newaxis]

# Display resultant array shape
print("Result:\n",res.shape)