17Dec, 2023
Python: A Deep Dive into Data Structures for Efficient Programming

Welcome to our journey into the heart of Python programming, where we’ll unravel the mysteries of data structures and unveil the secrets to writing efficient code. In this blog, we’ll explore the rich landscape of Python’s data structures, understanding how they work under the hood and mastering the art of leveraging them to optimize your programs.

What is data structure in Python

In Python, a data structure is like a container that helps organize and store data. It could be a list, holding items in a specific order, or a dictionary, which stores data in key-value pairs. These structures make it easier to manage and manipulate information in your programs. Think of them as tools that help you arrange and access your data efficiently, like a well-organized toolbox for a programmer.

Various data structure type in Python

Lists:

  • Ordered collection of items.
  • Mutable (can be changed).
  • Example: my_list = [1, 2, 3]


Tuples:

  • Similar to lists but immutable (cannot be changed).
  • Often used for fixed collections.
    Example: my_tuple = (4, 5, 6)


Dictionaries:

  • Unordered collection of key-value pairs.
  • Used for quick data retrieval.
  • Example: my_dict = {‘apple’: 3, ‘banana’: 5}


Sets:

  • Unordered collection of unique items.
  • Useful for operations like union and intersection.
  • Example: my_set = {1, 2, 3}


Strings:

  • Sequence of characters.
    Immutable, like tuples.
    Example: my_string = “Hello”


Arrays (from the array module):

  • Homogeneous data structure, similar to lists.
  • Requires importing the array module.
  • Example: import array; my_array = array.array(‘i’, [1, 2, 3])


Queues (from the queue module):

  • Implements FIFO (First-In-First-Out) order.
  • Useful for managing tasks in a specific order.
    Example: import queue; my_queue = queue.Queue()


Stacks (from the collections module):

  • Implements LIFO (Last-In-First-Out) order.
  • Convenient for managing items in reverse order.
  • Example: import collections; my_stack = collections.deque()


Linked Lists (custom implementation):

  • Series of elements where each element points to the next one.
  • Dynamic and efficient for insertion and deletion.
  • Example: Custom implementation using classes and pointers.
    Heaps (from the heapq module):

Binary tree-based data structure.

  • Efficient for finding and removing the smallest (or largest) element.
  • Example: import heapq; my_heap = [1, 3, 5]; heapq.heapify(my_heap)

Creating a List:

# Creating an empty list
my_list = []

# Creating a list with initial values
my_list = [1, 2, 3, 4, 5]

# Lists can contain different types of elements
mixed_list = [1, 'two', 3.0, True]
Accessing Elements: 
# Accessing elements by index
print(my_list[0])  # Output: 1
print(my_list[2])  # Output: 3

# Negative indexing
print(my_list[-1]) # Output: 5 (last element)

Slicing: 

# Slicing a list
print(my_list[1:3])  # Output: [2, 3]

# Omitting start and end indices
print(my_list[:3])   # Output: [1, 2, 3] (from beginning to index 2)
print(my_list[2:])   # Output: [3, 4, 5] (from index 2 to end)

Modifying Lists: 

# Appending elements to a list
my_list.append(6)   # my_list is now [1, 2, 3, 4, 5, 6]

# Extending a list with another list
my_list.extend([7, 8, 9])   # my_list is now [1, 2, 3, 4, 5, 6, 7, 8, 9]

# Inserting elements at a specific position
my_list.insert(2, 'new')    # my_list is now [1, 2, 'new', 3, 4, 5, 6, 7, 8, 9]

# Removing elements by value
my_list.remove('new')       # my_list is now [1, 2, 3, 4, 5, 6, 7, 8, 9]

# Removing elements by index
del my_list[0]              # my_list is now [2, 3, 4, 5, 6, 7, 8, 9]

# Clearing the entire list
my_list.clear()             # my_list is now []

Other Operations: 

# Length of a list
print(len(my_list))   # Output: 0

# Checking if an element is in a list
print(2 in my_list)   # Output: False

# Reversing a list
reversed_list = my_list[::-1]

Tuples

In Python, a tuple is a collection of ordered and immutable elements. This means once a tuple is created, its elements cannot be changed, added, or removed. Tuples are commonly used for grouping related data. Here’s how you can work with tuples in Python:

Creating a Tuple:



# Creating an empty tuple
my_tuple = ()

# Creating a tuple with values
my_tuple = (1, 2, 3, 4, 5)

# Tuples can contain different types of elements
mixed_tuple = (1, 'two', 3.0, True)

# You can also create a tuple without parentheses
another_tuple = 1, 2, 3

Accessing Elements: 

# Accessing elements by index
print(my_tuple[0])  # Output: 1
print(my_tuple[2])  # Output: 3

# Negative indexing
print(my_tuple[-1]) # Output: 5 (last element)

Slicing: 

# Slicing a tuple
print(my_tuple[1:3])  # Output: (2, 3)

# Omitting start and end indices
print(my_tuple[:3])   # Output: (1, 2, 3) (from beginning to index 2)
print(my_tuple[2:])   # Output: (3, 4, 5) (from index 2 to end)

Other Operations: 

# Length of a tuple
print(len(my_tuple))   # Output: 5

# Checking if an element is in a tuple
print(2 in my_tuple)   # Output: True

Immutable Nature: 

# Attempting to change a tuple (this will result in an error)
my_tuple[0] = 10  # TypeError: 'tuple' object does not support item assignment

Dictionaries

In Python, a dictionary is a collection of key-value pairs. Dictionaries are unordered, mutable, and can contain elements of different data types. Each key in a dictionary must be unique, and it is used to access its corresponding value. Here’s how you can work with dictionaries in Python:

Creating a Dictionary:

# Creating an empty dictionary
my_dict = {}

# Creating a dictionary with initial key-value pairs
my_dict = {'name': 'John', 'age': 30, 'city': 'New York'}

# Dictionaries can contain different types of values
mixed_dict = {'name': 'Alice', 'age': 25, 'is_student': True}

Accessing Elements: 

# Accessing values by key
print(my_dict['name'])  # Output: John
print(my_dict['age'])   # Output: 30

# If the key is not present, it will raise a KeyError
# You can use .get() method to avoid this
print(my_dict.get('city'))  # Output: New York
print(my_dict.get('occupation'))  # Output: None

Modifying and Adding Elements: 

# Modifying the value associated with a key
my_dict['age'] = 35

# Adding a new key-value pair
my_dict['occupation'] = 'Engineer'

# Updating multiple key-value pairs at once
my_dict.update({'city': 'San Francisco', 'age': 40})

Removing Elements:

# Removing a key-value pair
del my_dict['city']

# Removing a key-value pair using .pop() method (also returns the value)
removed_age = my_dict.pop('age')

# Removing all key-value pairs
my_dict.clear()

Other Operations:

# Length of a dictionary (number of key-value pairs)
print(len(my_dict))

# Checking if a key is present in the dictionary
print('name' in my_dict)  # Output: True

Set

In Python, a set is an unordered collection of unique elements. Sets are mutable, meaning you can add or remove elements, but the elements themselves must be immutable. Sets are commonly used for tasks involving membership testing, eliminating duplicate entries, and performing mathematical set operations such as union, intersection, difference, and symmetric difference. Here’s how you can work with sets in Python: 
# Creating an empty set
my_set = set()

# Creating a set with initial values
my_set = {1, 2, 3, 4, 5}

# Sets can also be created from other iterable types like lists
another_set = set([1, 2, 3])

Adding and Removing Elements: 

# Adding elements to a set
my_set.add(6)

# Adding multiple elements to a set
my_set.update([7, 8, 9])

# Removing elements from a set
my_set.remove(5)  # Raises KeyError if element not found
my_set.discard(8) # Does not raise an error if element not found

# Removing and returning an arbitrary element from the set
popped_element = my_set.pop()

Set Operations:

# Union of sets
set1 = {1, 2, 3}
set2 = {3, 4, 5}
union_set = set1.union(set2)  # {1, 2, 3, 4, 5}

# Intersection of sets
intersection_set = set1.intersection(set2)  # {3}

# Difference of sets
difference_set = set1.difference(set2)  # {1, 2}

# Symmetric difference of sets
symmetric_difference_set = set1.symmetric_difference(set2)  # {1, 2, 4, 5}

# Checking if a set is a subset or superset of another set
is_subset = set1.issubset(set2)
is_superset = set1.issuperset(set2)

String

Creating Strings:

# Single line string
single_quoted_string = 'Hello, World!'
double_quoted_string = "Hello, World!"

# Multi-line string using triple quotes
multi_line_string = '''This is a multi-line
string in Python.'''

# Raw string (treats backslashes as literal characters)
raw_string = r'C:\Users\John'

# Unicode string
unicode_string = 'H\u00e9llo'

Accessing Characters:

 # Accessing individual characters by index
print(single_quoted_string[0])  # Output: H
print(single_quoted_string[-1])  # Output: !

# Slicing strings
print(single_quoted_string[1:5])  # Output: ello
print(single_quoted_string[:5])   # Output: Hello
print(single_quoted_string[7:])   # Output: World!

String Methods:

# Converting to uppercase
uppercase_string = single_quoted_string.upper()

# Converting to lowercase
lowercase_string = double_quoted_string.lower()

# Finding substring
index = single_quoted_string.find(‘World’) # Returns the index where ‘World’ starts

# Replacing substring
replaced_string = single_quoted_string.replace(‘World’, ‘Universe’)

# Checking if string starts or ends with a specific substring
starts_with_hello = single_quoted_string.startswith(‘Hello’)
ends_with_world = single_quoted_string.endswith(‘World’)

String Formatting:

# Using f-strings (Python 3.6+)
name = 'Alice'
age = 30
formatted_string = f'My name is {name} and I am {age} years old.'

# Using format method
formatted_string = 'My name is {} and I am {} years old.'.format(name, age)

Array

In Python, the array module provides a way to create arrays which are similar to lists but are more efficient for storing large amounts of data of the same type. Arrays are a part of the Python standard library and are particularly useful when dealing with numerical data.

Importing the array Module: 

import array

Creating Arrays:

# Creating an array of integers
int_array = array.array('i', [1, 2, 3, 4, 5])

# Creating an array of floating-point numbers
float_array = array.array('f', [1.0, 2.5, 3.7])

# Creating an array of characters
char_array = array.array('c', b'hello')

Arrays (from the array module

Arrays (from the array module

Accessing Elements:

# Accessing elements by index
print(int_array[0])  # Output: 1
print(float_array[1])  # Output: 2.5
print(char_array[2])  # Output: l

Modifying Elements:# Modifying elements int_array[2] = 10

Array Methods:

# Appending elements to the end of the array
int_array.append(6)

# Extending the array with another iterable
int_array.extend([7, 8, 9])

# Inserting elements at a specific index
int_array.insert(2, 20)

# Removing the first occurrence of a value
int_array.remove(3)

# Removing and returning an element by index
popped_element = int_array.pop(3)

# Finding the index of the first occurrence of a value
index = int_array.index(5)

# Counting the occurrences of a value
count = int_array.count(2)

# Reversing the order of elements in the array
int_array.reverse()

# Sorting the elements of the array
int_array_sorted = sorted(int_array)

What application do data structure have

  • Database Optimization: Organizing data for faster retrieval.
  • Algorithm Efficiency: Enhancing speed in problem-solving.
  • Memory Management: Efficient use of system resources.
  • Network Routing: Facilitating data transfer in networks.
  • AI and Machine Learning: Representing and manipulating knowledge.
  • Graphical Applications: Managing complex data for user interfaces.

Give 3 reason why numpy array are better than list

Speed:

NumPy arrays are faster for numerical tasks because they’re designed to work efficiently with large datasets.


Memory Efficiency:

NumPy uses memory more effectively than regular lists, making it better for handling big sets of data without using too much computer memory.


Convenient Operations:

NumPy makes it easy to perform operations on entire arrays at once, simplifying code and improving performance. Lists in Python might need more code for similar tasks.

What is the difference between tuple and list?

Feature

Tuple

List

Mutability

Immutable (cannot be changed or modified)

Mutable (can be changed or modified)

Syntax

Defined by parentheses ()

Defined by square brackets []

Example

my_tuple = (1, 2, 3)

my_list = [1, 2, 3]

Methods             

Limited methods due to immutability

More methods available for modification

Use Cases

Used for fixed collections of items

Used for dynamic collections of items

Performance

Slightly faster than lists for iteration

Slower than tuples for iteration

Memory Usage

Generally less memory than equivalent lists

Generally more memory than equivalent tuples

Purpose

Suitable for data that shouldn’t change

Suitable for data that may need modification

Indexing and Slicing

Supports indexing and slicing

supports indexing, slicing, and modifying

What is the difference between an array and a python list?

Feature

Array

Python List

Data Type

Usually homogeneous (same data type)

Heterogeneous (can store different data types)

Mutability

Depends on the specific array implementation

Mutable (can be changed or modified)

Syntax

Depends on the specific array implementation

Defined by square brackets []

Example              

import array; my_array = array.array(‘i’, [1, 2, 3])

my_list = [1, 2, 3]

Methods

Limited methods for array operations

More methods available for modification and manipulation

Use Cases

Numerical computations, mathematical operations

General-purpose data storage and manipulation

Performance

Can be more memory-efficient for large datasets

May consume more memory due to flexibility and overhead

Purpose              

Specialized for specific tasks (e.g., numerical operations)

General-purpose data storage and manipulation

Indexing and Slicing

upports indexing and slicing

Supports indexing, slicing, and modifying

What are the advantages of using a Numpy array over a list?

  • Performance: NumPy arrays offer faster operations due to vectorization and efficient memory allocation.
  • Memory Efficiency: Contiguous memory storage makes NumPy more memory-efficient for large datasets.
  • Convenience: Supports multidimensional arrays, broadcasting, and concise syntax for operations.
  • Rich Functionality: Extensive mathematical and linear algebra functions for scientific computing.
    Interoperability
  •  Seamless integration with various scientific computing libraries.
  • Type Stability: Fixed data type ensures stability, useful for interfacing with other languages.
  • Parallel Computing: Optimized for parallel operations, taking advantage of multiple CPU cores.

How are 1d 2d and 3d array are created ?

import numpy as np

# 1D Array
array_1d = np.array([1, 2, 3, 4, 5])

# 2D Array
array_2d = np.array([[1, 2, 3], [4, 5, 6]])

# 3D Array
array_3d = np.array([[[1, 2, 3], [4, 5, 6]], [[7, 8, 9], [10, 11, 12]]])

# Display the arrays
print("1D Array:")
print(array_1d)

print("\n2D Array:")
print(array_2d)

print("\n3D Array:")
print(array_3d)

What is Slicing in Python ?

Slicing in Python refers to the technique of extracting a portion (or a slice) of a sequence, such as a string, list, or tuple. It allows you to obtain a subset of the elements from the original sequence. Slicing is accomplished using the colon (:) notation within square brackets []

  • sequence[start:stop:step]
  • start: The index of the first element in the slice (inclusive).
  • stop: The index of the first element not to be included in the slice (exclusive).
    step (optional): The step or stride between elements. It determines how many indices to skip.
    Here are some examples of slicing:

 

my_list = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

# Get elements from index 2 to 5 (exclusive)
subset = my_list[2:5]
print(subset)  # Output: [2, 3, 4]

# Get every second element from index 1 to 8
subset = my_list[1:8:2]
print(subset)  # Output: [1, 3, 5, 7]

Comparison between linear and non-linear data structures

 

Feature

Linear Data Structures

Non-Linear Data Structures

Elements Arrangement

Sequential or linear order.

Hierarchical or interconnected order.

Traversal

Straightforward linear traversal.

More complex traversal, often involving recursion or specialized algorithms.

Memory Utilization

ontiguous memory allocation.

Non-contiguous memory allocation.

Examples

Arrays, Linked Lists, Queues, Stacks.

Trees (Binary Trees, N-ary Trees), Graphs.

Relationship between Elements

Each element has a unique predecessor and successor.

No strict linear order; elements are interconnected or form hierarchi

Space Complexity

Generally requires less memory compared to non-linear structures.

May require more memory due to non-contiguous storage and additional pointers/links.

Flexibility

Limited flexibility in terms of relationships between elements.

Offers more flexibility for modeling complex relationships and hierarchical structures.

 

How to you randomize number in list ?

To randomize numbers in a list in Python, you can use the random.shuffle() function from the random module. This function shuffles the elements of a list in-place. Here’s an example:

import random

# Example list
my_list = [1, 2, 3, 4, 5]

# Randomize the list
random.shuffle(my_list)

# Display the randomized list
print("Randomized List:", my_list)