numpy.newaxis Method

This tutorial will discuss the numpy.newaxis method.

the numpy.newaxis Method

The numpy.newaxis method is an alias for the None, which is used for array indexing in Python. The most straightforward use of the numpy.newaxis is to add a new dimension to a NumPy array in Python. For example, converting a 1D array into a 2D array, converting a 2D array into a 3D array, and so on. We can also convert a 1D array to either a row matrix or a column matrix with the numpy.newaxis in Python. The following code example shows us how to transform a 1D array into a row matrix with the numpy.newaxis in Python.

import numpy as np

array = np.array([1, 2, 3, 4])
print(array.shape)

array = array[np.newaxis]
print(array.shape)

Output:

(4,)
(1, 4)

We transformed the 1D array array into a row matrix with the np.newaxis in the above code. We first created the 1D array array with the np.array() function. We then used the [np.newaxis] as the index of the array to return a row matrix. The following code example shows us how to transform a 1D array into a column matrix with the numpy.newaxis.

import numpy as np

array = np.array([1, 2, 3, 4])
print(array.shape)

array = array[:, np.newaxis]
print(array.shape)

Output:

(4,)
(4, 1)

We transformed the 1D array array into a column matrix with the np.newaxis in the above code. We first created the 1D array array with the np.array() function. We then used the [:, np.newaxis] as the index of the array to return a column matrix.

As we have mentioned previously, the numpy.newaxis is an alias for None. So, we can also perform both operations discussed above with the None in place of the numpy.newaxis. The following code example shows us how to transform a 1D array into a row matrix with the None in Python.

import numpy as np

array = np.array([1, 2, 3, 4])
print(array.shape)

array = array[None]
print(array.shape)

Output:

(4,)
(1, 4)

We transformed the 1D array array into a row matrix with the None in Python in the above code. We first created the 1D array array with the np.array() function. We then used the [None] as the index of the array to return a row matrix.

The following code example shows us how to transform a 1D array into a column matrix with the None in Python.

import numpy as np

array = np.array([1, 2, 3, 4])
print(array.shape)

array = array[:, None]
print(array.shape)

Output:

(4,)
(4, 1)

We transformed the 1D array array into a column matrix with the None in Python in the above code. We first created the 1D array array with the np.array() function. We then used the [:, None] as the index of the array to return a column matrix.

In conclusion, both numpy.newaxis, and None are the same and can be used in array indexing and slicing.