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Python Commandments

Reverse an array in Python

This method has no return value, but does reverse sort the elements of the list.

The reversed function returns a reversed iterator. list is the sequence of transformations and can be tuple, string, list or range.

reversed(list)

You can reverse list or reverse array (see bottom).

reverse a list

The program below reverses a list and several other sequences:

#!/usr/bin/python                                                                                                                                           
aList = [123, 'xyz', 'zara', 'abc', 'xyz']                                                                                                                  

aList.reverse()                                                                                                                                             
print("List : ", aList)                                                                                                                                     

# String                                                                                                                                                    
seqString = 'Python'                                                                                                                                        
print(list(reversed(seqString)))                                                                                                                            

# tuple                                                                                                                                                     
seqTuple = ('P', 'y', 't', 'h', 'o', 'n')                                                                                                                   
print(list(reversed(seqTuple)))                                                                                                                             

# range                                                                                                                                                     
seqRange = range(5, 9)                                                                                                                                      
print(list(reversed(seqRange)))                                                                                                                             

# List                                                                                                                                                      
seqList = [1, 2, 4, 3, 5]                                                                                                                                   
print(list(reversed(seqList)))

Results

List :  ['xyz', 'abc', 'zara', 'xyz', 123]
['n', 'o', 'h', 't', 'y', 'P']
['n', 'o', 'h', 't', 'y', 'P']
[8, 7, 6, 5]
[5, 3, 4, 2, 1]

reverse list example

Print the list backwards.

# Define an array of car brands
cars = ['bmw', 'audi', 'benz']

# Export raw data
print('Export raw data')
print(cars)

# Calling reverse() reverses the order
cars.reverse()

# Export data in reverse order
print('\n output flipped data')
print(cars)

Exporting raw data

['bmw', 'audi', 'benz']

Output of flipped data

['benz', 'audi', 'bmw']
reverse an array in python

python array reverse

There is a very simple way to reverse array (numpy) in python

import numpy as np
a = np.array([1,2,3,4,5,6])
b=a[::-1]
print(b)

Results:

[6, 5, 4, 3, 2, 1]

Alternatively, you can use the flipud function

import numpy as np
a = np.array([1,2,3,4,5,6])
b== np.flipud(ini_array) 
print(b)

The results are also

[6, 5, 4, 3, 2, 1]