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# Reversing a NumPy array

NumPy

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*schedule*Jul 1, 2022

local_offer Python●NumPy

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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:

```
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()
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):

```
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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Published by Arthur Yanagisawa

Edited by 0 others

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