Python Program to insert multiple elements into the array from the specified index

An array is a collection of homogeneous data elements stored in an organized way. Each data element in the array is identified by an index value. In Python, we can insert multiple elements at a specific index position using various approaches.

Arrays in Python

Python does not have a native array data structure, so we use the list data structure as an alternative ?

# Python list example
my_list = [10, 4, 11, 76, 99]
print(my_list)

[10, 4, 11, 76, 99]

We can also use the NumPy module to work with arrays ?

import numpy as np
arr = np.array([1, 2, 3, 4])
print(arr)

[1 2 3 4]

The indexing in Python starts from 0, so the array elements are accessed using their respective index values like 0, 1, 2, up to n1.

Input Output Scenarios

Let's see some examples of inserting multiple elements at specified index positions ?

# Example 1
Input array: [9, 3, 7, 1]
Output array: [9, 3, 6, 2, 10, 7, 1]
# Elements 6, 2, 10 inserted at index 2

# Example 2  
Input array: [2, 4, 6, 8, 1, 3, 9]
Output array: [1, 1, 1, 2, 4, 6, 8, 1, 3, 9]
# Elements 1, 1, 1 inserted at index 0

Using List Slicing

List slicing allows us to insert multiple elements at a specified index by assigning to an empty slice ?

numbers = [2, 3, 1, 4, 7, 5]
print("Original array:", numbers)

specified_index = 1
multiple_elements = [10, 11, 12]

# Insert elements using slice assignment
numbers[specified_index:specified_index] = multiple_elements

print("Array after inserting multiple elements:", numbers)

Original array: [2, 3, 1, 4, 7, 5]
Array after inserting multiple elements: [2, 10, 11, 12, 3, 1, 4, 7, 5]

Using List Concatenation

We can create a custom function using list slicing and concatenation to insert multiple elements at a specified position ?

def insert_elements(array, index, elements):
    return array[:index] + elements + array[index:]

numbers = [1, 2, 3, 4, 5, 6]
print("Original array:", numbers)

specified_index = 2
multiple_elements = [10, 20, 30]

# Insert elements using custom function
result = insert_elements(numbers, specified_index, multiple_elements)

print("Array after inserting multiple elements:", result)

Original array: [1, 2, 3, 4, 5, 6]
Array after inserting multiple elements: [1, 2, 10, 20, 30, 3, 4, 5, 6]

Using numpy.insert() Method

The numpy.insert() method provides a convenient way to insert multiple values at specified indices. The syntax is ?

numpy.insert(arr, obj, values, axis=None)

This method returns a copy of the input array with inserted values but does not modify the original array.

Example with Numbers

import numpy as np

arr = np.array([2, 4, 6, 8, 1, 3, 9])
print("Original array:", arr)

specified_index = 2
multiple_elements = [100, 200, 300]

# Insert elements using numpy.insert()
result = np.insert(arr, specified_index, multiple_elements)

print(f"Array after inserting elements at index {specified_index}:", result)

Original array: [2 4 6 8 1 3 9]
Array after inserting elements at index 2: [  2   4 100 200 300   6   8   1   3   9]

Example with Strings

import numpy as np

arr = np.array(['a', 'b', 'c', 'd'])
print("Original array:", arr)

specified_index = 0
multiple_elements = ['x', 'y', 'z']

# Insert string elements
result = np.insert(arr, specified_index, multiple_elements)

print(f"Array after inserting elements at index {specified_index}:", result)

Original array: ['a' 'b' 'c' 'd']
Array after inserting elements at index 0: ['x' 'y' 'z' 'a' 'b' 'c' 'd']

Comparison

Conclusion

Use list slicing for inplace insertion into Python lists. Use numpy.insert() for NumPy arrays and when working with numerical computations. Choose list concatenation when you need to preserve the original array.