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How to reverse a vector in numpy

Posted on February 7, 2023March 2, 2023 By Luke K

You can reverse a NumPy array using the [::-1] slicing syntax. This creates a new reversed array, leaving the original array unchanged.

Here’s an example of how to reverse a 1-D NumPy array:

How to reverse a vector

import numpy as np

a = np.array([1, 2, 3, 4, 5])
result = a[::-1]
print(result)
# Output: [5 4 3 2 1]

How to reverse a multi-dimensional array

If you want to reverse a multi-dimensional array, you can reverse each axis separately using slicing. For example, to reverse a 2-D array along the second axis (columns), you can do the following:

import numpy as np

a = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
result = a[:, ::-1]
print(result)
# Output:
# [[3 2 1]
#  [6 5 4]
#  [9 8 7]]

Note that the [::-1] slicing syntax works for any array shape and any number of dimensions, so you can use it to reverse arrays of any size and shape.

See also  How to convert array from float to int in Numpy?
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