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# Reversing a NumPy array

schedule Aug 12, 2023
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To reverse a NumPy array use the `flipud(~)` method for one-dimensional NumPy arrays and `fliplr(~)` for multi-dimensional NumPy arrays.

# Examples

## One-dimensional

Consider the following one-dimensional array:

``` a = np.array([1,2,3])a array([1, 2, 3]) ```

To reverse the order of the array:

``` np.flipud(a) array([3, 2, 1]) ```

Note here that a view object is returned. The view object shares the same memory as the original array meaning that changing one will also change the other. If this is not desired, create a copy of the array before using `flipud(~)` like so:

``` copy_a = a.copy()np.flipud(copy_a) array([3, 2, 1]) ```

## Multi-dimensional

Consider the following multi-dimensional array:

``` a = np.array([[1,2,3],[4,5,6],[7,8,9]])a array([[7, 8, 9], [4, 5, 6], [1, 2, 3]]) ```

To reverse the order of the array column-wise (horizontal flip):

``` np.fliplr(a) array([[3, 2, 1], [6, 5, 4], [9, 8, 7]]) ```

Note that this method is equivalent to `np.flip(a, axis=1)`, where `a` is the input array.

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