## Python reverse NumPy array

In this Python tutorial, we will discuss Python reverse NumPy array with a few examples like below:

Python reverse array sort reverse
Python numpy inverse array
Python numpy invert array
Python numpy flip array

## Python reverse numpy array

In this section, we will discuss Python reverse numpy array. We can easily use the list slicing() method to reverse an array in Python.
We actually create a new list in the reverse order as that of the original one.
Let’s take an example to check how to implement a reverse numpy array
Basically there are many ways to check reverse numpy array.
Using list slicing method
Using flip() function
Using reverse() function
Using flipud() method
Using fliplr() function
Using length() function

## Using List slicing

In this method first, we will create a NumPy array and then use the slicing method.

Example:

import numpy as np

arr= np.array([1, 2, 3, 6, 4, 5])
result = arr[::-1]

print(“Reverse array”,(result))

Here is the Screenshot of the following given code

Python reverse numpy array

## Using flip() function

In this method, we can easily use the Python function flip() to reverse an original array.
The flip() function is used to reverse the order of elements in an array along the given axis.
The flip() function is defined under numpy, which can be imported as import numpy as np, and we can create multidimensional arrays and derive other mathematical statistics with the help of numpy, which is a library in Python.
The shape of the array is preserved, but the elements are reordered.

Syntax:

Here is the Syntax of the flip() function

numpy.flip
(
arr,
axis=None
)

It consists of few parameters

arr: input array

axis: The default, axis=None, will flip over all of the axes of the input array. If axis is negative it counts from the last to the first axis.

Example:

Let’s take an example to check how to implement a reverse NumPy array by using the flip() function.

import numpy as np

arr= np.array([9, 8, 3, 6, 2, 1])
result = np.flip(arr)

print(“Reverse array”,(result))

In the above example, we will first import a NumPy library and create a NumPy array using the function np. array. After that create a variable and assign the function np. fill in which passes an argument as an array and print the result. The output will display in the form of reverse order.

Here is the Screenshot of the following given code

Python reverse numpy array by the flip method

## Using reverse() function

In this method, we can easily use the function reverse() to reverse an original array.
The reversed() function returns the reversed iterator of the given sequence.
It reverses an array at its original location, hence doesn’t require extra space for storing the results.
It is an inbuilt method in Python programming language that reverses objects of list in place.

Example:

Let’s take an example to check how to implement a reverse NumPy array by using the reverse() function.

import array

arr=array.array(‘i’,[4,5,9,1,9,3])
print(arr)

#reversing using reverse()
arr.reverse()
print(“Reversed Array:”,arr)

In the above example first, we will import an array library and then create an original array and pass string and array as an argument.

Here is the Screenshot of the following given code

Python reverse numpy array reverse method

## Using flipud() method

In this method, we can easily use the flipud() method to reverse an original array.
The flipud() function is used to flip an given array in the up/down direction.
Flip the entries in each column in the up/down direction.
The flipud() function is used to shift the function from up to down.
The ud means Up / Down. The np.flipud() returns a view. Because a view shares memory with the original array, changing one value changes the other.

Syntax:

Here is the Syntax of flipud() method

numpy.flipud
(
array
)

It consists of few parameters

array: input array

Returns: Flipped array in up-down direction

Example:

Let’s take an example to check how to implement a reverse numpy array by using the flipud() method.

import numpy as np

arr= np.array([9, 8, 3, 6, 2, 1])
result = np.flipud(arr)

print(“Reverse array”,(result))

In the above example, we will first import a NumPy library and create a NumPy array using the function np. array. After that create a variable and assign the function np.flipud in which passes an argument as an array and prints the result. The output will display in the form of reverse order.

Here is the Screenshot of the following given code

Python reverse numpy array by flipud method

## Using fliplr() function

In this method, we can easily use the fliplr() function to reverse an original array.
The np.fliplr() function flips the array(entries in each column) in left-right direction. The numpy flipr() function accepts an array as an argument and returns the array the same array as flipped in the left-right direction.
It reverse the order of elements along axis 1 (left/right).

Syntax:

Here is the Syntax of fliplr() function

numpy.fliplr
(
arr
)

It consists of few parameters

arr: input array

Returns: It returns an output array with the columns reversed. Since the operation is returned the operation

Example:

Let’s take an example to check how to implement a reverse NumPy array by using the fliplr() function.

import numpy as np

arr= np.array([[3, 5, 6, 7, 2, 1],
[2,5,6,7,8,9]])
result = np.fliplr(arr)

print(“Reverse array”,(result))

Here is the Screenshot of the following given code

Python reverse numpy array fliplr method

## Using length() function

In this method, we can easily use the length() function.
We are going to begin by pointing to the first element within our given list. Take a start index variable which is equal to zero. After that we are going to the last element of our list which is end_index and that’s going to equal the length of our list.
So the length function itself is going to return as an integer value

Example:

Let’s take an example to check how to implement a reverse NumPy array by using the length() function.

def reverse(nums):

start_index = 0
end_index = len(nums)-1

while end_index > start_index:
nums[start_index],nums[end_index] = nums[end_index],nums[start_index]
start_index = start_index + 1
end_index = end_index -1

if __name__ == ‘__main__’:
n = [1,2,3,4,5]
reverse(n)
print(n)

Here is the Screenshot of the following given code

Python reverse numpy array using the length function

## Python reverse array sort reverse

In this section, we will discuss Python reverse array sort reverse.
In Numpy, the sort() function does not allow us to sort an array in descending order. Instead, we can reverse an array utilizing list slicing in Python, after it has been sorted in ascending order.
The slice notation [::1] with default start and stop indices and negative step size -1 reverses a given list.
Use slicing notation s[start:stop:step] to access every step-th element starting from index start (included) and ending in index stop (excluded).

Example:

import numpy as np
arr = np.array([2, 5, 1, 6, 7, 2, 4])

sort_arr = np.sort(arr)
# Reverse the sorted array
reve_arr = sort_arr[::-1]
print(sort_arr)
print(reve_arr)

In the above example first we will import a numpy library and create an array using the np.array function. After that create a variable and arrange the elements using np.sort() function.
Reverse the sorted array using slicing method and print the result.

Here is the Screenshot of the following given code

Python reverse numpy array reverse method

## Python numpy inverse array

In this section, we will discuss Python numpy inverse array.
For matrix inverse, we need to use numpy.linalg.inv() function.
This function will inverse the given matrix. The inverse of a matrix is such that if it is multiplied by the original matrix, it results in identity matrix.
It consists of one parameter that is A and A can be a matrix.
Python provides an easy method to calculate the inverse of the matrix. The function numpy.linalg.inv() is available in the Python numpy library.

Syntax:

numpy.linalg.inv(a)

Example:

Let’s take an example to check how to inverse an array in python

import numpy as np

a = np.array([[4,3],[2,7]])
inverse_matrix = (np.linalg.inv(a))
print(inverse_matrix)

In the above example first, we will import a numpy library and create an array using the np. array function. After that create a variable and assign the function np.linalg and display the result.

Here is the Screenshot of the following given code

Python numpy inverse array

## Another method to check Python numpy inverse array

In this method, we can easily use the function np.matrix to inverse the elements of an array.
It Returns a matrix from an array-like object, or from a string of data.
A matrix is a specialized 2-D array that retains its 2-D nature through operations.
In this method we use the I attribute to inverse the elements of a given matrices.

Syntax:

Here is the Syntax of np.matrix()

numpy.matrix
(
data,
dtype=None,
copy=True
)

It consists of few parameters

data: it is interpreted as a matrix with commas or spaces separating columns, and semicolons separating rows.

dtype: Data type of the matrix

Example:

Let’s take an example to check how to inverse an array in python

import numpy as np

m = np.matrix([[4,6],[7,8]])
print (m.I)

Here is the Screenshot of the following given code

Python numpy inverse array matrix method

## Python numpy invert array

In this section, we will discuss Python numpy invert array. Here we can easily use the function numpy.invert().
This function is used to compute the bit-wise inversion of an array element wise.
It Computes the bit-wise NOT of the underlying binary representation of the integers in the input arrays.

Syntax:

Here is the Syntax of numpy.invert()

numpy.invert
(
x,
out=None,
Where=True,
casting=’same_kind’,
order=’K’,
dtype=None
)

It consists of few parameters

X: input array (Only integer and boolean types are handled).

Out: Its an optional parameter. A location into which the result is stored. If provided, it must have a shape that the inputs broadcast.

Where: This condition is broadcast over the input. At locations where the condition is True, the out array will be set to the ufunc result.

Example:

Let’s take an example to check how to implement a numpy invert array

import numpy as np

arr= np.array([4, 5, 5, 6, 2, 1])
result = np.invert(arr)

print(“Invert array”,(result))

Here is the Screenshot of the following given code

Python numpy invert array

## Python numpy flip array

In this section, we will discuss Python numpy flip array. For this we can easily use the function numpy.flip().
This function reverses the order of array elements along the specified axis, preserving the shape of the array.
The shape of the array is preserved, but the elements are reordered.

Syntax:

Here is the Syntax of the flip() function

numpy.flip
(
arr,
axis=None
)

Example:

Let’s take an example to check how to implement a reverse NumPy array by using the flip() function.

import numpy as np

arr2= np.array([4, 2, 3, 2, 1, 8])
res = np.flip(arr2)

print(res)

Python numpy flip array

You may like the following Python NumPy tutorials:

In this Python tutorial, we will discuss Python reverse NumPy array with a few examples like below:

Python reverse array sort reverse
Python numpy inverse array
Python numpy invert array
Python numpy flip array 