Python - Append at Front and Remove from Rear

We are given a list we need to append element in front and remove from rear. For example, a = [10, 20, 30] we need to add 5 in front and remove from rear so that resultant output should be [5, 10, 20].

Using insert

Using insert in Python allows us to add an element at the front of a list by specifying index 0. To remove from the rear we use pop method without arguments which removes and returns last element of list.

[5, 10, 20]

Explanation:

• a.insert(0, 5) inserts the element 5 at the front of the list.
• a.pop() removes the last element (30), resulting in the modified list [5, 10, 20].

Using list slicing

List slicing enables appending at the front by combining [element] + list. Removing from rear can be done using list[:-1] to exclude the last element..

[5, 10, 20]

Explanation:

• Element 5 is appended to the front by creating a new list [5] and concatenating it with the original list a.
• Last element is removed using slicing (a[:-1]), which creates a new list excluding the last element of a.

Using collections.deque

collections.deque is a double-ended queue that allows fast appending and popping from both ends. It provides appendleft() to add an element at front and pop() to remove an element from the rear efficiently.

[5, 10, 20]

Explanation:

• a.appendleft(5) adds element 5 to the front of the deque.
• a.pop() removes last element from the deque, resulting in the modified list [5, 10, 20].