Arrays in Python

November 26, 2022

Arrays

In this tutorial, you’ll learn about the Python Arrays module, the difference between arrays and lists, and how and when to use them with the help of examples.
In this tutorial, we will focus on a module named Array. The Array module allows us to store a collection of numeric values.

To learn the Implementation of Array using List visit our Python List Tutorial.

array in python

Type Code

Type codes are characters assigned to different types of data types. This is not much used in Python Programming Language as the interpreter automatically understands the data type and dynamically increases the size but in the case of an array in python, we use type code to constrain the type of elements to be stored in the array.

Different types of Type codes are :-

Type Code Python

Creating Array

In python, a module named array needs to be imported for the implementation of the array and to use inbuilt functions for the Arrays.

import array

Afterward, we need to assign a name and create an array by passing type code ( data type code which we want to store ) and a list storing the values to be stored in an array. The type Code of float values is d.

a = array.array('d', [1.5, 2.5, 3.5]

Syntax:

import module_name
variable_name = module_name.array( type_code, list_of_values)

Accessing Array Elements

We use indices to access elements of an array:

Run

import array as arr
a = arr.array('i', [2, 4, 6, 8])

print("First element:", a[0])
print("Second element:", a[1])
print("Last element:", a[-1])

Slicing Python Arrays

We can access a range of items in an array by using the slicing operator :
Run 
import array as arr

numbers_list = [1, 2, 3, 4, 5, 6, 7, 8, 9]
numbers_array = arr.array('i', numbers_list)

print(numbers_array[1:4]) # 2rd to 4th
print(numbers_array[:3])  # beginning to 4th
print(numbers_array[5:])  # 6th to end
print(numbers_array[:])   # beginning to end

Changing and Adding Elements

Arrays are mutable, their elements can be changed similarly to lists.
Run 
import array as arr

numbers = arr.array('i', [1, 2, 3, 5, 7, 10])

# changing first element
numbers[0] = 0    
print(numbers)     # Output: array('i', [0, 2, 3, 5, 7, 10])

# changing 3rd to 5th element
numbers[2:5] = arr.array('i', [4, 6, 8])   
print(numbers)     # Output: array('i', [0, 2, 4, 6, 8, 10])
We can add one item to the array using the append() method, or add several items using the extend() method.
Run 
import array as arr

numbers = arr.array('i', [1, 2, 3])

numbers.append(4)
print(numbers)     # Output: array('i', [1, 2, 3, 4])

# extend() appends iterable to the end of the array
numbers.extend([5, 6, 7])
print(numbers)     # Output: array('i', [1, 2, 3, 4, 5, 6, 7])
We can also concatenate two arrays using + operator.
Run 
import array as arr

odd = arr.array('i', [1, 3, 5])
even = arr.array('i', [2, 4, 6])

numbers = arr.array('i')   # creating empty array of integer
numbers = odd + even

print(numbers)

Removing Python Array Elements

We can delete one or more items from an array using Python’s del statement.
Run 
import array as arr

number = arr.array('i', [1, 2, 3, 3, 4])

del number[2]  # removing third element
print(number)  # Output: array('i', [1, 2, 3, 4])

del number  # deleting entire array
print(number)  # Error: array is not defined
We can use the remove() method to remove the given item, and pop() method to remove an item at the given index.
Run 
import array as arr

numbers = arr.array('i', [10, 11, 12, 12, 13])

numbers.remove(12)
print(numbers)   # Output: array('i', [10, 11, 12, 13])

print(numbers.pop(2))   # Output: 12
print(numbers)   # Output: array('i', [10, 11, 13])

Lists Vs Arrays

Array

If you create arrays using the array module, all elements of the array must be of the same type.
Run 
import array as arr
# Error
a = arr.array('d', [1, 1.5, 'A', "Prep"])

List

In Python, we can treat lists as arrays. However, we cannot constrain the type of elements stored in a list. For example:

Run 
# elements of different types
a = [1, 1.5, 'A', "Prep"]
Python Arrays