NumPy transpose()

Summary: in this tutorial, you’ll learn how to use the numpy transpose() function to reverse the axes of an array.

Introduction to the numpy transpose() function #

The numpy transpose() function reverses the axes of an array. Here’s the syntax of the transpose() function:

numpy.transpose(a, axes=None)Code language: Python (python)

In this syntax:

• a is an input array. It can be a numpy array or any object that can be converted to a numpy array.
• axes is a tuple or a list that contains a permutation of [0,1,..,N-1] where N is the number of axes of the array a.

The transpose() function returns the array a with its axes permuted.

The transpose() function is equivalent to:

• ndarray.T property method that returns an array transposed.
• ndarray.transpose(*axes) method that returns an array transposed.

NumPy transpose() function examples #

Let’s take some examples of using the transpose() function.

1) Using transpose() function with 1-D array example #

The following example uses the transpose() function with 1-D array:

import numpy as np

a = np.array([1, 2, 3])
b = np.transpose(a)
print(b)Code language: Python (python)

Output:

[1 2 3]Code language: Python (python)

The transpose() function has no effect on a 1-D array because a transposed vector is simply the same vector.

2) Using numpy transpose() function with 2-D array example #

The following example uses the transpose() function to transpose a 2-D array (or a matrix):

import numpy as np

a = np.array([
    [1, 2, 3],
    [4, 5, 6]
])

b = np.transpose(a)
print(b)Code language: Python (python)

Output:

[[1 4]
 [2 5]
 [3 6]]Code language: Python (python)

In this example, the transpose() function transpose a (2,3) array. Basically, it swaps rows and columns of the array.

After the transposition, the first row of array a becomes the first column of the transposed array b, the second row of array a becomes the second column of the transposed array b.

Summary #

• Use the transpose() to transpose an array.