NumPy flip()

import numpy as np

# create an array
array1 = np.array([0, 1, 2, 3, 4])

# flip the elements of array1
array2 = np.flip(array1)

print(array2)

# Output: [4 3 2 1 0]

flip() Syntax

The syntax of flip() is:

numpy.flip(array, axis = None)

flip() Arguments

The flip() method takes two arguments:

• array - an array with elements to be flipped
• axis(optional) - axis to flip ( None or int or tuple )

flip() Return Value

The flip() method returns the array with elements reversed.

Example 1: Flip a 2-D Array

A 2-D array can be flipped on two axes. If the array is flipped on axis 0, it is reversed vertically and if the array is flipped on axis 1, it is reversed horizontally.

import numpy as np

# create an array
array1 = np.array([[0, 1, 2], [3, 4, 5], [6, 7, 8]])

# flip the elements of array1
array2 = np.flip(array1)

# flip  array1 vertically
array3 = np.flip(array1, axis = 0)

# flip  array1 horizontally
array4 = np.flip(array1, axis = 1)

print('\n Flipped Array: \n', array2)
print('\n Array flipped along axis 0\n', array3)
print('\n Array flipped along axis 1\n', array4)

Output

Flipped Array: 
[[8 7 6]
[5 4 3]
[2 1 0]]

Array flipped along axis 0
[[6 7 8]
[3 4 5]
[0 1 2]]

Array flipped along axis 1
[[2 1 0]
[5 4 3]
[8 7 6]]

Here, we haven't passed axis in array2, so the array is flattened, flipped, and reshaped back to its original shape.

Example 2: Flip a 3-D Array on Multiple Axes

import numpy as np

# create an array
array1 = np.array([[[0, 1], [2, 3]],   
   		   [[4, 5], [6, 7]]])

# flip the elements of array1 along axis 0
array2 = np.flip(array1, axis = 0)

# flip the elements of array1 along axis 1
array3 = np.flip(array1, axis = 1)

# flip the elements of array1 along both axis 0 and 1
array4 = np.flip(array1, (0, 1))

print('\n Array flipped on axis 0: \n', array2)
print('\n Array flipped on axis 1: \n', array3)
print('\n Array flipped on axes 0 and 1: \n', array4)

Output

Array flipped on axis 0: 
[[[4 5]
  [6 7]]

 [[0 1]
  [2 3]]]

Array flipped on axis 1: 
[[[4 5]
 [6 7]]

 [[0 1]
  [2 3]]]

Array flipped on axes 0 and 1: 
[[[6 7]
  [4 5]]

 [[2 3]
  [0 1]]]

Example 3: Flip with flipup() and fliplr()

Instead of using the axis parameter, we can simply use flipud() to flip vertically and fliplr() to flip horizontally.

import numpy as np

# create an array
array1 = np.array([[0, 1], [2, 3]])

# flip the elements of array1 vertically
array2 = np.flipud(array1)

# flip the elements of array1 horizontally
array3 = np.fliplr(array1)

print('\n Array flipped vertically : \n',array2)
print('\n Array flipped horizontally : \n',array3)

Output

Array flipped vertically : 
[[2 3]
 [0 1]]

Array flipped horizontally : 
[[1 0]
 [3 2]]