Insert element at given location in array(list) in Python

In this tutorial, we will learn writing the python program to insert an element at the given position of an array (list in case of python) and print the array (list).

Problem Statement

Our problem statement is, for a given array(list) we have to add an element at the given position (index).

For example:

Case 1: if the given array (list) is [1, 2, 3, 4] and the user gives input 9 to add at index 2.

              The output should be [1, 2, 9, 3, 4].

Case 2: if the given array (list) is [9, 2, 4, 8] and the user gives input 10 to add at index 1.

               The output should be [9, 10, 2, 4, 8].

Our logic to insert an element at a given location of an array(list)

• Our program will take two inputs from the user, one is the elements and the other is the location ( position or index) of the element where the user wants the element to insert.
•  Then, use insert() built-in method with the user inputs as an argument to insert new element at given location. After insertion print the output.

Python code to insert an element at a given location of an array(list)

Program 1: Using the insert() Method

This is the most straightforward method provided by Python’s list data structure to insert elements at a specific position. insert() Method: The insert() method is used to place the element at the desired index. The elements at and beyond this index are shifted rightward.

# given array (list)
arr = [1, 2, 3, 4, 5]
num=int(input("Enter a number to insert in array : "))
index=int(input("Enter a index to insert value : "))
if index >= len(arr):
    print("please enter index smaller than",len(arr))
else:
    # insering element ‘num’ at ‘index’ position
    arr.insert(index, num)  
print("Array after inserting",num,"=",arr)

Output 1:

Enter a number to insert in array : 5
Enter a index to insert value : 2 
Array after inserting 5 = [1, 2, 5, 3, 4, 5]

Explanation:

For the given array (list) [1, 2, 3, 4, 5], the user inputs element 5 to add at the index 2 of the array (list). using the insert() method, our program will easily add element 5 at the desired location of the list and returns the updated list.

Output 2:

Enter a number to insert in array : 5
Enter a index to insert value : 2 
Array after inserting 5 = [1, 2, 5, 3, 4, 5]

Explanation:

For the given array (list) [1, 2, 3, 4, 5], the user inputs element 10 to add at the index 4 of the array (list). using the insert() method, our program will easily add element 10 at the desired location of the list and returns the updated list.

Program 2: Using Slicing

This method involves using slicing to construct a new list with the new element included at the desired position. Python lists can be sliced to create sublists. The new list is constructed by concatenating the part before the desired index, the new element (as a list), and the part after the index.

arr = [1, 2, 3, 4, 5]
num=int(input("Enter a number to insert in array : "))
index=int(input("Enter a index to insert value : "))
new_arrays = arr[:index] + [num] + arr[index:]
print("Array after inserting",num,"=",new_arrays)

Output

Enter a number to insert in array : 6
Enter a index to insert value : 2
Array after inserting 6 = [1, 2, 6, 3, 4, 5]

Each of these methods leverages Python’s flexible and dynamic handling of lists to insert elements. The choice of method depends on the specific needs for clarity, performance, and memory usage in your application.