# numpy.rollaxis() – The NumPy rollaxis Python Function

## Introduction to NumPy rollaxis Python Function

Guide to NumPy rollaxis Python Function – The numpy.rollaxis() function reverses the provided axis until it reaches a specified location.

Syntax:

`numpy.rollaxis(arr, axis, start=0)`

Parameters:

• arr : [ndarray] Input array.
• axis : [int] The axis to roll backward. The positions of the other axes do not change relative to one another.
• start : [int, optional] The axis is rolled until it lies before this position. The default, 0, results in a “complete” roll.

Return: [ndarray] In earlier NumPy versions, arr is returned only if the order of the axes is changed, otherwise the input array is returned. For NumPy >= 1.10.0, a view of arr is always return.

## Code Examples of NumPy rollaxis Python Function

Example 01:

``````# welcome to softhunt.net
# Python program explaining
# numpy.rollaxis() function

# importing numpy as np
import numpy as np

arr = np.ones((4, 3, 2, 1))

softhunt = np.rollaxis(arr, 3, 1).shape

print (softhunt)``````

Output:

`(4, 1, 3, 2)`

Note: These programs will not run in online IDEs. Please test them on your systems to see how they operate.

Example 02:

``````# welcome to softhunt.net
# Python program explaining
# numpy.rollaxis() function

# importing numpy as np
import numpy as np

arr = np.ones((4, 3, 2, 1))

softhunt = np.rollaxis(arr, 2).shape

print (softhunt)``````

Output:

`(2, 4, 3, 1)`

Note: These programs will not run in online IDEs. Please test them on your systems to see how they operate.

## FAQs

### How do I roll a NumPy array?

The numpy.roll() function moves elements in an array along a given axis. Essentially, the items of the input array are shifted. It is roll back to the initial position if an element is roll first to the final place.

### Difference between NumPy moveaxis and rollaxis

moveaxis: The numpy.moveaxis() function repositions the axes of an array. The order of the other axes remains unchanged.

rollaxis: The numpy.rollaxis() function reverses the provided axis until it reaches a specified location.

### What does NumPy roll do?

Array items are roll along a specified axis. Rolling elements are reintroduce at the initial position if they roll past the last place.

## NumPy rollaxis Python Function: Conclusion

That’s all for this article, if you have any confusion contact us through our website or email us at [email protected] or by using LinkedIn. And make sure you check out our NumPy tutorials.

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1. numpy.moveaxis() – The NumPy moveaxis Python Function