Reverse List in Python

Sometimes we need to reverse the list in Python. In this tutorial, we will learn how to reverse a list in Python.

1. Using the list reverse method

The list.reverse() method will reverse the elements of the list in place.

Syntax of the list reverse method :

list.reverse()

Arguments: Reverse method does not take any parameters.

Returns: Does not return any value, however it updates the list in place.

Let’s see the pros and cons of this method.

Pros:

• It is a fast operation, it does not require extra memory. We are not creating copy of the list.
• It is more readable.

Cons:

• Since it is an in-place operation it overwrites the original sort order.

Example

A simple example of list.reverse().

#Create a list of even numbers
even_numbers = [2,4,6,8,10]

# Reverse the list
even_numbers.reverse()

print(f"Reversed list {even_numbers}")

Output

Reversed list: [10, 8, 6, 4, 2]

2. Reverse list using the list slicing trick

Another way to reverse the list using the [: :-1] list slicing trick. List slicing syntax is [start : stop : step], to reverse the list we will use step size as -1; we can write it as list[ : :-1].

Example

# Create a list of devices
devices = ["printer","keyboard","mouse"]

#Reverse using list slicing
reversed_devices = devices[::-1]

print(f"Reversed list: {reversed_devices}")

Output

Reversed list: ['mouse', 'keyboard', 'printer']

Let’s see the pros and cons of this method.

Pros:

• It does not modify the original list.

Cons:

• It takes more memory and creates a shallow copy of the list.
• List slicing is an advanced feature so beginners may feel a bit difficult to use.

3. Reverse list using the reversed function

To reverse a list we can use the inbuilt reversed function. The syntax of the reversed function is

reversed(seq)

Parameters: Sequence ( strings, lists, tuples).

Returns: Reversed iterator.

Example

#Create a list of  numbers
numbers = [1,2,3,4,5]

# Reverse the list
reversed_numbers = list(reversed(numbers))

print(f"Reversed list: {reversed_numbers}")

Output

Reversed list: [5, 4, 3, 2, 1]

Here revered list iterator is converted to a list using “list(reversed(numbers))”.

We can iterate the reversed list as shown below:

#Create a list of  numbers
numbers = [1,2,3,4,5]

for number in reversed(numbers):
  print(number)

Output

5
4
3
2
1

This method has some advantages:

• It doesn’t modify the original list.
• It only returns the reversed iterator, sometimes we might need to convert it to a list.

Conclusion

That’s all about the three different ways to reverse a list in Python.