Python Program to Reverse an Array

Write a Python Program to reverse the given Numpy Array. We can use the slicing technique with a negative value to get the Numpy Array reverse. In this example, we used the same to reverse the numeric and string arrays.

import numpy as np

orgarr = np.array([15, 20, 50, 40, 78, 99, 248])
print("Original Numeric Numpy Array Items = ", orgarr)

revarr = orgarr[::-1]
print("After Reversing Numeric Numpy Array = ", revarr)

orgstrarr = np.array(['UK', 'India', 'USA', 'Japan'])
print("Original String Numpy Array Items = ", orgstrarr)

revstrarr = orgstrarr[::-1]
print("After Reversing String Numpy Array = ", revstrarr)
Python Program to Reverse an Array 1

Python Program to Reverse an Array using While loop

This example uses the temporary variable to shift the numeric array items and reverse them.

import numpy as np

orgarr = np.array([14, 27, 99, 50, 65, 18, 195, 100])

j = len(orgarr) - 1
i = 0

while(i < j):
    temp = orgarr[i]
    orgarr[i] = orgarr[j]
    orgarr[j] = temp
    i += 1
    j -= 1

print(orgarr)
[100 195  18  65  50  99  27  14]

Reverse an Array Using functions

In this Numpy Array example, we created a function (def reverseArray(orgarr, number)) that reverses the array passed to it.

# using functions
import numpy as np

def reverseArray(orgarr, number) :
    j = number - 1
    i = 0
    
    while(i < j):
        temp = orgarr[i]
        orgarr[i] = orgarr[j]
        orgarr[j] = temp
        i += 1
        j -= 1


arrList = []
number = int(input("Enter the Total Array Items = "))
for i in range(1, number + 1):
    value = int(input("Enter the %d Array value = " %i))
    arrList.append(value)

orgarr = np.array(arrList)
print("Original  = ", orgarr)

reverseArray(orgarr, number) 
print("After  = ", orgarr)
Python Program to Reverse an Array using while loop and functions

Reverse array items using recursion

In this program, we created a recursive function to Reverse an Array (reverseArray(orgarr, i + 1, j – 1)) with updated values.

import numpy as np

def reverseArray(orgarr, i, j) :
   if(i < j):
        temp = orgarr[i]
        orgarr[i] = orgarr[j]
        orgarr[j] = temp
        reverseArray(orgarr, i + 1, j - 1)
        

orgarr = np.array([22, 44, 87, 538, 89, 120, 197])
print("Original Numeric Numpy Array Items = ", orgarr)

reverseArray(orgarr, 0, (len(orgarr) - 1))
print("After Reversing Numeric Numpy Array = ", orgarr)
Python Program to Reverse an Array using recursion