Python program to add an element to an array

An array is a collection of elements of the same data type. Each element in the array is identified by an index value. It is the simplest data structure and we can easily add or remove elements.

Arrays in Python

Python has no specific data structure to represent arrays. Here we can list the array using .

 [9, 3, 1, 6, 9]

We can process arrays in python using array or NumPy module.

array('i', [1, 2, 3, 4])

The above array is an integer array defined by the array module.

In the same way, we can also use the NumPy module to define Numpy arrays.

array([1, 2, 3, 4])

Indices in python start from 0. All array elements above are also indexed starting from 0, 1,.., (n-1).

Input and output scenarios

Suppose we have an input array containing integer values. The resulting array will have one element appended.

Input array:
A = [1, 5, 3, 6]
Output array:
[1, 5, 3, 6, 2]

Integer element 2 is appended to the end of the given array.

In the following article, we have seen various ways to append elements to an array in Python.

Use list data structure

Since we are using List as an array, we can append elements to the array using the list.append() method.

grammar

list.append(element) 

It adds an element to the end of the list. Equivalent to a[len(a):] = [x].

Example

lst = [1, 2, 3, 4, 5, 6] 
print ("The original array is: ",lst) 
print() 

# append an element 
lst.append(9)
print ("The resultant array is: ",lst) 

Output

The original array is:  [1, 2, 3, 4, 5, 6]

The resultant array is:  [1, 2, 3, 4, 5, 6, 9]

Element 9 is appended to the array and added to the end of the array.

Using the array module

The array module in Python allows us to create an array and represent an array compactly. To initially use the array module, we need to import the array module.

grammar

array.append(x) 

Append a new item with value x to the end of the array.

Example

import array
 
# creating array
int_array = array.array('i', [1, 2, 3, 4])
print ("The original array is: ",int_array) 
print() 

# append an element 
int_array.append(0)
print ("The resultant array is: ",int_array) 

Output

The original array is:  array('i', [1, 2, 3, 4])

The resultant array is:  array('i', [1, 2, 3, 4, 0])

int_array objects are created with an integer type specified. If we try to append any other type element to the array object then it will throw an error like below.

TypeError - An integer argument was expected, but a floating point number was obtained

Using the NumPy module

By using the numpy library, we can easily create arrays using the numpy.array() method. Similarly, we can also append an element to an array using the numpy.append() method.

grammar

numpy.append(array, element) 

This method appends an element to the end of the array. It creates a new array, which can be a copy of the old array, and appends elements so that the original array remains unchanged.

Example

In this example, we will use a for loop to iterate over the string array elements.

import numpy
 
# creating array
array = numpy.array([1, 2, 3, 4])
print ("The original array is: ", array) 
print() 

# append an element 
result = numpy.append(array, 9)
print ("The resultant array is: ", result) 

Output

The original array is:  [1 2 3 4]

The resultant array is:  [1 2 3 4 9]

Here the original array remains unchanged and the resulting array has been updated with new elements.

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