Declaring an Array in Python

An array is a container used to store the same type of elements such as integer, float, and character type. An Array is one of the most important parts of data structures. In arrays, elements are stored in a contiguous location in a memory. We can access the array elements by indexing from 0 to (size of array – 1). Python does not have built-in support for arrays as available in programming languages like C, C++, and JAVA, however, we can use arrays in Python using different ways that we are going to learn in this article.

Declare an Array in Python

• Declare array using the list in Python.
• Declare array using the array module in Python.
• Declare array using NumPy module in Python.

Declare Array Using the List in Python

In Python, arrays are not supported instead List is used to store the element like in arrays. The list can store elements of different types. We can access the elements in a list using indexing as in arrays. So, the list can be used as an array but the only condition is all the elements should be of the same type.

Example: Here, we have declared an array using list with some interger values in it. We print the values of an array using indexing with the help of for loop. After that we insert the one more element at the end of list using append() function and modify the value at index ‘0’ in array. Now, we print array again and we can see in the modified array in an output.

Python3

# Declaring arrays using list in Python
array = [12, 34, 45, 32, 54]

for i in range(0, len(array)):
  print(array[i], end=" ")

# Inserting element in array
array.append(99);

# Modifying element in an array
array[0] = 100;

print("\nArray after modification :")

for i in range(0, len(array)):
  print(array[i], end=" ")

Output

12 34 45 32 54 
Array after modification :
100 34 45 32 54 99 

Declare Array Using the Array Module in Python

In Python, array module is available to use arrays that behave exactly same as in other languages like C, C++, and Java. It defines an object type which can compactly represent an array of primary values such as integers, characters, and floating point numbers.

Syntax to Declare an array

Variable_Name = array(typecode, [element1, element2, …., elementn])

Here,

• Variable_Name – It is the name of an array.
• typecode – It specifies the type of elements to be stored in an array.
• [] – Inside square bracket we can mention the element to be stored in array while declaration.

Example: In the below code, firstly we have import the array module and then we declare an array1 of interger type using array() function. After that we have print the values of array1.

Python3

import array as arr

# Declaring an array
array1 = arr.array('i', [10, 20, 30, 40, 50])

# Printing array1
for i in range(0, len(array1)):
  print(array1[i], end=" ")

Output

10 20 30 40 50 

Create NumPy Array

NumPy is a Python’s popular library used for working with arrays. NumPy arrays are more optimized than Python lists and optimization plays a crucial role while doing programming.

Example: In the below code, first we have import NumPy module then we have declared different types of arrays such as 1D, 2D, and 3D array using array() function of NumPy and then print them.

Python3

import numpy as np

# Declare 1D array
array1 = np.array([10, 23, 34, 33, 45])

print("Print 1D array: ")
print(array1)

# Declare 2D array
array2 = np.array([[1,2,3,4,5],[6,7,8,9,10]])

print("\nPrint 2D array: ")
print(array2)

# Declare 3D array
array3 = np.array([[[1,2,3,4,5],[6,7,8,9,10]],
                   [[11,12,13,14,15],[16,17,18,19,20]]])

print("\nPrint 3D array: ")
print(array3)

Ouput: