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id python-array
title Array in Python
sidebar_label Array in Python
sidebar_position 9
tags
Python
Array in Python
Introduction of python
Python Syntax
Variables
Operators
Type Casting
String

Arrays in Python

An Array in Python is a data structure that stores multiple elements of the same data type in contiguous memory locations.
Arrays are ordered, mutable, and type-restricted, making them more memory-efficient than lists for large numeric data.

In Python, arrays are provided by the built-in array module, which must be imported before use.

Creating an Array

You create an array using the array() constructor from the array module.

import array

# Empty array of integers
empty_array = array.array('i', [])

# Array of Integers
numbers = array.array('i', [1, 2, 3, 4, 5])

# Array of Floats
floats = array.array('f', [1.1, 2.2, 3.3])

print(numbers)  # array('i', [1, 2, 3, 4, 5])

Type Codes

Arrays in Python require a type code to specify the element type:

Type Code C Type Python Type Size (bytes)
'i' signed int int 2 or 4
'I' unsigned int int 2 or 4
'f' float float 4
'd' double float 8
'b' signed char int 1
'B' unsigned char int 1
'u' Py_UNICODE Unicode 2

Indexing

Just like lists, arrays use zero-based indexing.

nums = array.array('i', [10, 20, 30, 40, 50])

print(nums[0])   # 10
print(nums[2])   # 30
print(nums[-1])  # 50

Slicing

You can slice arrays to get sub-arrays.

print(nums[1:4])   # array('i', [20, 30, 40])
print(nums[:3])    # array('i', [10, 20, 30])
print(nums[::2])   # array('i', [10, 30, 50])

Syntax:

array[start:stop:step]

Modifying Elements

Arrays are mutable, so you can change elements:

nums[1] = 99
print(nums)  # array('i', [10, 99, 30, 40, 50])

Array Methods

Python's array module provides several useful methods:

Method Description
append(x) Adds an element to the end
insert(i, x) Inserts an element at index i
extend(iterable) Adds elements from another iterable
remove(x) Removes the first occurrence of the item
pop([i]) Removes and returns the item at index i
index(x) Returns the index of the first occurrence of the item
count(x) Counts how many times the item appears
reverse() Reverses the array
buffer_info() Returns a tuple (memory address, length)
tobytes() Converts the array to a bytes object
frombytes(b) Appends items from a bytes object

Examples

append()

nums = array.array('i', [1, 2, 3])
nums.append(4)
print(nums)  # array('i', [1, 2, 3, 4])

insert()

nums.insert(1, 100)
print(nums)  # array('i', [1, 100, 2, 3, 4])

extend()

nums.extend([5, 6])
print(nums)  # array('i', [1, 100, 2, 3, 4, 5, 6])

remove() and pop()

nums.remove(100)
print(nums)  # array('i', [1, 2, 3, 4, 5, 6])

nums.pop()   # Removes last element
print(nums)  # array('i', [1, 2, 3, 4, 5])

nums.pop(2)  # Removes index 2
print(nums)  # array('i', [1, 2, 4, 5])

Iterating Through an Array

Using a for loop:

for num in nums:
    print(num)

Using indices:

for i in range(len(nums)):
    print(i, nums[i])

Membership Test

Check if an element exists in an array:

print(10 in nums)     # True or False
print(100 not in nums) # True or False

Array from List

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

Copying Arrays

Assigning directly creates a reference:

a = array.array('i', [1, 2, 3])
b = a
b.append(4)
print(a)  # array('i', [1, 2, 3, 4])

To make an independent copy:

c = array.array(a.typecode, a)
c.append(5)

print(a)  # array('i', [1, 2, 3, 4])
print(c)  # array('i', [1, 2, 3, 4, 5])

Practice Questions

  1. Basic Traversal

    Q1: Write a Python program to traverse an array and print each element on a new line.

  2. Maximum Element

    Q2: Write a Python program to find the maximum and minimum elements in an array without using built-in functions.

  3. Array Reversal

    Q3: Write a Python program to reverse an array without using slicing or the reverse() method.

  4. Insertion Operation

    Q4: Write a Python program to insert an element at a specific index in an array.

  5. Deletion Operation

    Q5: Write a Python program to delete an element from a given index in an array.

  6. Search Element

    Q6: Write a Python program to search for a given element in an array and print its index if found, otherwise print "Not Found".

  7. Sum of Elements

    Q7: Write a Python program to find the sum of all elements in an array without using the sum() function.

  8. Second Largest Element

    Q8: Write a Python program to find the second largest element in an array.

Conclusion

Python Arrays are useful when you need to store large amounts of numeric data of the same type efficiently.
They provide faster performance and smaller memory footprint compared to lists for numerical operations.