Python

# NumPy np.flip()

The flip function in NumPy allows you to reverse the order of elements in an array along a specified axis while preserving the array’s shape.

Let us explore how this function works and how to use it.

## Function Syntax

The function syntax is as depicted below:

numpy.flip(m, axis=None)

## Parameters

The function accepts the following parameters:

1. m – refers to the input array or array_like object.
2. axis – defines the axis along which the elements are reversed. By default, the function will flatten the array and reverse the elements.

## Return Value

The function will return the array of m with the elements reversed but the shape preserved.

## Example #1

The below code uses the flip() function to reverse the provided array.

# import numpy
import numpy as np
arr = np.arange(6).reshape(2,3)
print(arr)
print(np.flip(arr, axis=None))

In the example above, we reverse the elements of the 2d array. The resulting array is as shown:

[[0 1 2]
[3 4 5]]
[[5 4 3]
[2 1 0]]

## Example #2

To flip the array horizontally, we set the axis to zero, as shown in the code below:

arr = np.arange(6).reshape(2,3)
print(f"original: {arr}")
print(f"flipped: {np.flip(arr, axis=0)}")

The code above should return the flipped array as:

original:
[[0 1 2]
[3 4 5]]
flipped:
[[3 4 5]
[0 1 2]]

## Example #3

To reverse the elements vertically, set the axis as one. The code illustration is as shown:

arr = np.arange(6).reshape(2,3)
print(f"original: {arr}")
print(f"flipped: {np.flip(arr, axis=1)}")

The resulting output is as shown:

original:
[[0 1 2]
[3 4 5]]
flipped:
[[2 1 0]
[5 4 3]]

## Conclusion

In this tutorial, we have covered the syntax of the flip() function and saw detailed examples of how the function works along various array axes.