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Python program for Reversing a List

In this tutorial, we will discuss the different approaches for reversing a list in Python. For a given list, we have to reverse the order of all the elements in the list and print the reversed list.

In Python, there are three ways for reversing a list, we will be discussing all the ways in detail.

For a given list, our program will return the list after reversing:

Input: [ 'Study', 'tonight', 1]

Output: [1, 'tonight', 'study']

Input: [14, 5, 2, 8, 19]

Output: [19, 8, 2, 5, 14]

Approach to Reverse the list in Python

In Python, there are various ways of reversing a list. We will discuss three of them in this tutorial.

  1. Using reverse() method
  2. Accessing in reverse order
  3. Reversing using slicing

Let us look at these approaches in detail separately

Approach 1: reverse() method

In this approach, we will use a built-in method reverse() which will reverse a given list. This method will modify the existing list and copy the elements in reverse order.

Algorithm

Step 1- Initialise list

Step 2- Use list.reverse()

Step 3- Print reversed list

Python Program 1

Look at the program to understand the implementation of the above-mentioned approach.

#reversing a list
#using reverse()
list = ['Study','tonight', 1, 2, 3]
print("Existing list",list)
# reversing
list.reverse()
print("After reversing all elements")
print(list)


Existing list ['Study', 'tonight', 1, 2, 3]
After reversing all elements
[3, 2, 1, 'tonight', 'Study']

Approach 2: accessing in reverse order

In this approach, we will access the elements of a list in reverse order and then print the list. To access all the elements in reverse, we will use reversed() function which returns the iterator to access each element in reverse order.

Algorithm

Step 1- Initialise list

Step 2- Run a loop for each element

Step 3- Use reversed() to get iteration of elements in reverse order

Step 4- Print elements

Python Program 2

Look at the program to understand the implementation of the above-mentioned approach.

#reversing a list

list = ['Study','tonight',11, 5, 6]
print("Existing list",list)
# printing in reverse
print("After reverse all elements")
#using reversed()
for i in reversed(list):
    print(i)


Existing list ['Study', 'tonight', 11, 5, 6]
After reversing all elements
6
5
11
tonight
Study

Approach 3: slicing in Python

In this approach, we will declare a new list and then use the slicing operator (:) to copy the elements in reverse order in the new list.

Algorithm

Step 1- Initialise a function to reverse list

Step 2- Declare new list

Step 3- Store elements in lew list in reverse order

Step 4- Print reversed list

Python Program 3

Look at the program to understand the implementation of the above-mentioned approach.

#reversing a list
#function to reverse list
def rev(list):
    # creating new list
    new_list = list[::-1]
    return new_list

list = [2, 45, 21, 15, 6]
print("Existing list",list)
print("After reversing all elements")
print(rev(list))


Existing list [2, 45, 21, 15, 6]
After reversing all elements
[6, 15, 21, 45, 2]

Conclusion

In this tutorial, we have learned three ways of reversing a list in Python. We have also learned how to use built-in functions like reverse() and reversed() to get the desired list. We have also used the concept of slicing.