🐍 Tip of the day for experienced Python developers
📌 Use decorators with parameters — a powerful technique for logging, control, caching, and custom checks.
Example: a logger that can set the logging level with an argument:
✅ Why you need it:
The decorator is flexibly adjustable;
Suitable for prod tracing and debugging in maiden;
Retains the signature and docstring thanks to @functools.wraps.
⚠️ Tip: avoid nesting >2 levels and always write tests for decorator behavior.
Python gives you tools that look like magic, but work stably if you know how to use them.
📌 Use decorators with parameters — a powerful technique for logging, control, caching, and custom checks.
Example: a logger that can set the logging level with an argument:
import functools
import logging
def log(level=logging.INFO):
def decorator(func):
@functools.wraps(func)
def wrapper(*args, **kwargs):
logging.log(level, f"Call {func.__name__} with args={args}, kwargs={kwargs}")
return func(*args, **kwargs)
return wrapper
return decorator
@log(logging. DEBUG)
def compute(x, y):
return x + y
✅ Why you need it:
The decorator is flexibly adjustable;
Suitable for prod tracing and debugging in maiden;
Retains the signature and docstring thanks to @functools.wraps.
⚠️ Tip: avoid nesting >2 levels and always write tests for decorator behavior.
Python gives you tools that look like magic, but work stably if you know how to use them.
❤10
Forwarded from Machine Learning with Python
This channels is for Programmers, Coders, Software Engineers.
0️⃣ Python
1️⃣ Data Science
2️⃣ Machine Learning
3️⃣ Data Visualization
4️⃣ Artificial Intelligence
5️⃣ Data Analysis
6️⃣ Statistics
7️⃣ Deep Learning
8️⃣ programming Languages
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✅ https://t.me/Codeprogrammer
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Topic: Python Classes and Objects — Basics of Object-Oriented Programming
Python supports object-oriented programming (OOP), allowing you to model real-world entities using classes and objects.
---
Defining a Class
---
Creating Objects
---
Key Concepts
• Class: Blueprint for creating objects.
• Object: Instance of a class.
•
•
---
Adding Methods
---
Inheritance
• Allows a class to inherit attributes and methods from another class.
---
Summary
• Classes and objects are core to Python OOP.
• Use
• Initialize attrinitith
• Objects are instances of classes.
• Inheritance enables code reuse and polymorphism.
---
#Python #OOP #Classes #Objects #ProgrammingConcepts
Python supports object-oriented programming (OOP), allowing you to model real-world entities using classes and objects.
---
Defining a Class
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def greet(self):
print(f"Hello, my name is {self.name} and I am {self.age} years old.")
---
Creating Objects
person1 = Person("Alice", 30)
person1.greet() # Output: Hello, my name is Alice and I am 30 years old.---
Key Concepts
• Class: Blueprint for creating objects.
• Object: Instance of a class.
•
__init__ method: Constructor that initializes object attributes.•
self parameter: Refers to the current object instance.---
Adding Methods
class Circle:
def __init__(self, radius):
self.radius = radius
def area(self):
return 3.1416 * self.radius ** 2
circle = Circle(5)
print(circle.area()) # Output: 78.54
---
Inheritance
• Allows a class to inherit attributes and methods from another class.
class Animal:
def speak(self):
print("Animal speaks")
class Dog(Animal):
def speak(self):
print("Woof!")
dog = Dog()
dog.speak() # Output: Woof!
---
Summary
• Classes and objects are core to Python OOP.
• Use
class keyword to define classes.• Initialize attrinitith
__init__ method.• Objects are instances of classes.
• Inheritance enables code reuse and polymorphism.
---
#Python #OOP #Classes #Objects #ProgrammingConcepts
❤3
Topic: Python Exception Handling — Managing Errors Gracefully
---
Why Handle Exceptions?
• To prevent your program from crashing unexpectedly.
• To provide meaningful error messages or recovery actions.
---
Basic Try-Except Block
---
Catching Multiple Exceptions
---
Using Else and Finally
• else block runs if no exceptions occur.
• finally block always runs, used for cleanup.
---
Raising Exceptions
• You can raise exceptions manually using raise.
---
Custom Exceptions
• Create your own exception classes by inheriting from Exception.
---
Summary
• Use try-except to catch and handle errors.
• Use else and finally for additional control.
• Raise exceptions to signal errors.
• Define custom exceptions for specific needs.
---
#Python #ExceptionHandling #Errors #Debugging #ProgrammingTips
---
Why Handle Exceptions?
• To prevent your program from crashing unexpectedly.
• To provide meaningful error messages or recovery actions.
---
Basic Try-Except Block
try:
result = 10 / 0
except ZeroDivisionError:
print("Cannot divide by zero!")
---
Catching Multiple Exceptions
try:
x = int(input("Enter a number: "))
result = 10 / x
except (ValueError, ZeroDivisionError) as e:
print(f"Error occurred: {e}")
---
Using Else and Finally
• else block runs if no exceptions occur.
• finally block always runs, used for cleanup.
try:
file = open("data.txt", "r")
data = file.read()
except FileNotFoundError:
print("File not found.")
else:
print("File read successfully.")
finally:
file.close()
---
Raising Exceptions
• You can raise exceptions manually using raise.
def check_age(age):
if age < 0:
raise ValueError("Age cannot be negative.")
check_age(-1)
---
Custom Exceptions
• Create your own exception classes by inheriting from Exception.
class MyError(Exception):
pass
def do_something():
raise MyError("Something went wrong!")
try:
do_something()
except MyError as e:
print(e)
---
Summary
• Use try-except to catch and handle errors.
• Use else and finally for additional control.
• Raise exceptions to signal errors.
• Define custom exceptions for specific needs.
---
#Python #ExceptionHandling #Errors #Debugging #ProgrammingTips
❤2
Topic: Python List vs Tuple — Differences and Use Cases
---
Key Differences
• Lists are mutable — you can change, add, or remove elements.
• Tuples are immutable — once created, they cannot be changed.
---
Creating Lists and Tuples
---
When to Use Each
• Use lists when you need a collection that can change over time.
• Use tuples when the collection should remain constant, providing safer and faster data handling.
---
Common Tuple Uses
• Returning multiple values from a function.
• Using as keys in dictionaries (since tuples are hashable, lists are not).
---
Converting Between Lists and Tuples
---
Performance Considerations
• Tuples are slightly faster than lists due to immutability.
---
Summary
• Lists: mutable, dynamic collections.
• Tuples: immutable, fixed collections.
• Choose based on whether data should change or stay constant.
---
#Python #Lists #Tuples #DataStructures #ProgrammingTips
https://t.me/DataScience4
---
Key Differences
• Lists are mutable — you can change, add, or remove elements.
• Tuples are immutable — once created, they cannot be changed.
---
Creating Lists and Tuples
my_list = [1, 2, 3]
my_tuple = (1, 2, 3)
---
When to Use Each
• Use lists when you need a collection that can change over time.
• Use tuples when the collection should remain constant, providing safer and faster data handling.
---
Common Tuple Uses
• Returning multiple values from a function.
def get_coordinates():
return (10, 20)
x, y = get_coordinates()
• Using as keys in dictionaries (since tuples are hashable, lists are not).
---
Converting Between Lists and Tuples
list_to_tuple = tuple(my_list)
tuple_to_list = list(my_tuple)
---
Performance Considerations
• Tuples are slightly faster than lists due to immutability.
---
Summary
• Lists: mutable, dynamic collections.
• Tuples: immutable, fixed collections.
• Choose based on whether data should change or stay constant.
---
#Python #Lists #Tuples #DataStructures #ProgrammingTips
https://t.me/DataScience4
❤1
Topic: Mastering Recursion — From Basics to Advanced Applications
---
What is Recursion?
• Recursion is a technique where a function calls itself to solve smaller instances of a problem until reaching a base case.
---
Basic Structure
• Every recursive function needs:
* A base case to stop recursion.
* A recursive case that breaks the problem into smaller parts.
---
Simple Example: Fibonacci Numbers
---
Drawbacks of Naive Recursion
• Repeated calculations cause exponential time complexity.
• Can cause stack overflow on large inputs.
---
Improving Recursion: Memoization
• Store results of subproblems to avoid repeated work.
---
Advanced Concepts
• Tail Recursion: Recursive call is the last operation. Python does not optimize tail calls but understanding it is important.
• Divide and Conquer Algorithms: Recursion breaks problems into subproblems (e.g., Merge Sort, Quick Sort).
---
Example: Merge Sort
---
Exercise
• Implement a recursive function to solve the Tower of Hanoi problem for *n* disks and print the moves.
---
#Algorithms #Recursion #Memoization #DivideAndConquer #CodingExercise
https://t.me/DataScience4
---
What is Recursion?
• Recursion is a technique where a function calls itself to solve smaller instances of a problem until reaching a base case.
---
Basic Structure
• Every recursive function needs:
* A base case to stop recursion.
* A recursive case that breaks the problem into smaller parts.
---
Simple Example: Fibonacci Numbers
def fibonacci(n):
if n <= 1:
return n # base case
else:
return fibonacci(n-1) + fibonacci(n-2) # recursive case
---
Drawbacks of Naive Recursion
• Repeated calculations cause exponential time complexity.
• Can cause stack overflow on large inputs.
---
Improving Recursion: Memoization
• Store results of subproblems to avoid repeated work.
memo = {}
def fib_memo(n):
if n in memo:
return memo[n]
if n <= 1:
memo[n] = n
else:
memo[n] = fib_memo(n-1) + fib_memo(n-2)
return memo[n]---
Advanced Concepts
• Tail Recursion: Recursive call is the last operation. Python does not optimize tail calls but understanding it is important.
• Divide and Conquer Algorithms: Recursion breaks problems into subproblems (e.g., Merge Sort, Quick Sort).
---
Example: Merge Sort
def merge_sort(arr):
if len(arr) <= 1:
return arr
mid = len(arr) // 2
left = merge_sort(arr[:mid])
right = merge_sort(arr[mid:])
return merge(left, right)
def merge(left, right):
result = []
i = j = 0
while i < len(left) and j < len(right):
if left[i] < right[j]:
result.append(left[i])
i += 1
else:
result.append(right[j])
j += 1
result.extend(left[i:])
result.extend(right[j:])
return result
---
Exercise
• Implement a recursive function to solve the Tower of Hanoi problem for *n* disks and print the moves.
---
#Algorithms #Recursion #Memoization #DivideAndConquer #CodingExercise
https://t.me/DataScience4
❤4
Topic: Python File Handling — Reading, Writing, and Managing Files (Beginner to Advanced)
---
What is File Handling?
• File handling allows Python programs to read from and write to external files — such as
• Python uses built-in functions like open(), read(), and write() to interact with files.
---
Opening a File
---
Using with Statement (Best Practice)
• Automatically handles file closing:
---
File Modes
• "r" — read (default)
• "w" — write (creates or overwrites)
• "a" — append (adds to the end)
• "x" — create (fails if file exists)
• "b" — binary mode
• "t" — text mode (default)
---
Writing to Files
• Note:
---
Appending to Files
---
Reading Line by Line
---
Working with File Paths
• Use os.path or pathlib for platform-independent paths.
---
Advanced Tip: Reading and Writing CSV Files
---
Summary
• Use open() with correct mode to read/write files.
• Prefer with statement to manage files safely.
• Use libraries like csv, json, or pickle for structured data.
• Always handle exceptions like FileNotFoundError for robust file operations.
---
Exercise
• Write a Python program that reads a list of names from
---
#Python #FileHandling #ReadWrite #DataProcessing #ProgrammingTips
https://t.me/DataScience4
---
What is File Handling?
• File handling allows Python programs to read from and write to external files — such as
.txt, .csv, .json, etc.• Python uses built-in functions like open(), read(), and write() to interact with files.
---
Opening a File
file = open("example.txt", "r") # "r" = read mode
content = file.read()
file.close()---
Using with Statement (Best Practice)
• Automatically handles file closing:
with open("example.txt", "r") as file:
content = file.read()---
File Modes
• "r" — read (default)
• "w" — write (creates or overwrites)
• "a" — append (adds to the end)
• "x" — create (fails if file exists)
• "b" — binary mode
• "t" — text mode (default)
---
Writing to Files
with open("output.txt", "w") as file:
file.write("Hello, world!")• Note:
"w" overwrites existing content.---
Appending to Files
with open("output.txt", "a") as file:
file.write("\nNew line added.")---
Reading Line by Line
with open("example.txt", "r") as file:
for line in file:
print(line.strip())---
Working with File Paths
• Use os.path or pathlib for platform-independent paths.
from pathlib import Path
file_path = Path("folder") / "file.txt"
with open(file_path, "r") as f:
print(f.read())
---
Advanced Tip: Reading and Writing CSV Files
import csv
with open("data.csv", "w", newline="") as file:
writer = csv.writer(file)
writer.writerow(["name", "age"])
writer.writerow(["Alice", 30])
with open("data.csv", "r") as file:
reader = csv.reader(file)
for row in reader:
print(row)---
Summary
• Use open() with correct mode to read/write files.
• Prefer with statement to manage files safely.
• Use libraries like csv, json, or pickle for structured data.
• Always handle exceptions like FileNotFoundError for robust file operations.
---
Exercise
• Write a Python program that reads a list of names from
names.txt, sorts them alphabetically, and saves the result in sorted_names.txt.---
#Python #FileHandling #ReadWrite #DataProcessing #ProgrammingTips
https://t.me/DataScience4
❤3
Topic: Django Models and ORM — From Basics to Advanced Queries
---
What is a Model in Django?
• A model in Django is a Python class that defines the structure of your database table. Each model maps to a table, and each attribute represents a column.
• Django uses its ORM (Object-Relational Mapping) to interact with the database using Python code instead of SQL.
---
Creating Your First Model
---
Making Migrations
• Create and apply migrations to sync models with the database:
---
Using the Model
---
Model Field Types
• CharField, TextField, IntegerField, FloatField, DateField, DateTimeField, BooleanField, EmailField, and more.
---
Meta Class for Model Options
---
Relationships Between Models
• One-to-Many (ForeignKey)
• Many-to-Many (ManyToManyField)
• One-to-One (OneToOneField)
---
Advanced ORM Queries
---
Summary
• Django models define your database structure.
• The ORM allows you to query and manipulate data using Python.
• Supports relationships, complex filtering, ordering, and aggregation.
---
Exercise
• Create two models:
1. Add a new book.
2. List all books by a specific author.
3. Delete books published before the year 2000.
---
#Django #WebDevelopment #ORM #DatabaseModels #DjangoTips
https://t.me/DataScience4
---
What is a Model in Django?
• A model in Django is a Python class that defines the structure of your database table. Each model maps to a table, and each attribute represents a column.
• Django uses its ORM (Object-Relational Mapping) to interact with the database using Python code instead of SQL.
---
Creating Your First Model
from django.db import models
class Book(models.Model):
title = models.CharField(max_length=200)
author = models.CharField(max_length=100)
published_date = models.DateField()
pages = models.IntegerField()
---
Making Migrations
• Create and apply migrations to sync models with the database:
python manage.py makemigrations
python manage.py migrate
---
Using the Model
# Creating a new record
book = Book(title="1984", author="George Orwell", published_date="1949-06-08", pages=328)
book.save()
# Fetching all books
books = Book.objects.all()
# Filtering
orwell_books = Book.objects.filter(author="George Orwell")
# Getting one object
book = Book.objects.get(id=1)
# Updating
book.title = "Animal Farm"
book.save()
# Deleting
book.delete()
---
Model Field Types
• CharField, TextField, IntegerField, FloatField, DateField, DateTimeField, BooleanField, EmailField, and more.
---
Meta Class for Model Options
class Book(models.Model):
title = models.CharField(max_length=200)
class Meta:
ordering = ['title'] # default ordering by title
---
Relationships Between Models
• One-to-Many (ForeignKey)
• Many-to-Many (ManyToManyField)
• One-to-One (OneToOneField)
class Author(models.Model):
name = models.CharField(max_length=100)
class Book(models.Model):
title = models.CharField(max_length=200)
author = models.ForeignKey(Author, on_delete=models.CASCADE)
---
Advanced ORM Queries
# Complex filters
books = Book.objects.filter(published_date__year__gte=2000, pages__lte=300)
# Exclude
books = Book.objects.exclude(author="J.K. Rowling")
# Ordering
books = Book.objects.order_by("-published_date")
# Count
total = Book.objects.count()
---
Summary
• Django models define your database structure.
• The ORM allows you to query and manipulate data using Python.
• Supports relationships, complex filtering, ordering, and aggregation.
---
Exercise
• Create two models:
Author and Book. Link them using a foreign key. Then, write views that:1. Add a new book.
2. List all books by a specific author.
3. Delete books published before the year 2000.
---
#Django #WebDevelopment #ORM #DatabaseModels #DjangoTips
https://t.me/DataScience4
❤4
Topic: Django ORM – Advanced Queries, Aggregations, and Query Optimization (Part 2)
---
1. Aggregation Functions
• Django provides built-in functions for aggregating data.
---
2. Grouping and Annotating
• annotate() is used to compute values for each row (e.g., totals per group).
---
3. Complex Lookups with Q Objects
• Use Q for OR, AND, and NOT conditions.
---
4. Selecting Specific Fields
• Use values() or values\_list() to retrieve specific fields.
---
5. Related Model Queries
• Use select\_related and prefetch\_related to optimize related data access.
---
6. Raw SQL Queries (When Necessary)
---
7. Performance Tips
• Use only() or defer() to limit retrieved fields.
• Avoid chaining queries in loops.
• Use bulk\_create, bulk\_update for inserting/updating many records.
---
Summary
• Use aggregate(), annotate(), and Q objects for powerful filtering.
• Fetch only what you need using values, only, and select\_related.
• Optimize queries by reducing database hits and using Django’s ORM efficiently.
---
Exercise
• Write a Django query that returns all authors with more than 5 books, sorted by the number of books (descending). Then print their name and book count.
---
#Django #ORM #AdvancedQueries #QueryOptimization #WebDevelopment
https://t.me/DataScience4
---
1. Aggregation Functions
• Django provides built-in functions for aggregating data.
from django.db.models import Avg, Sum, Max, Min, Count
# Average number of pages
avg_pages = Book.objects.aggregate(Avg("pages"))
# Total number of pages
total_pages = Book.objects.aggregate(Sum("pages"))
# Count of books per author
book_counts = Book.objects.values("author").annotate(total=Count("id"))
---
2. Grouping and Annotating
• annotate() is used to compute values for each row (e.g., totals per group).
# Number of books per author
from django.db.models import Count
authors = Author.objects.annotate(book_count=Count("book"))
for author in authors:
print(author.name, author.book_count)
---
3. Complex Lookups with Q Objects
• Use Q for OR, AND, and NOT conditions.
from django.db.models import Q
# Books with title containing 'war' OR author name 'Leo Tolstoy'
books = Book.objects.filter(Q(title__icontains="war") | Q(author__name="Leo Tolstoy"))
# Books not published in 2023
books = Book.objects.filter(~Q(published_date__year=2023))
---
4. Selecting Specific Fields
• Use values() or values\_list() to retrieve specific fields.
# Dictionary of titles and authors
data = Book.objects.values("title", "author__name")
# List of titles
titles = Book.objects.values_list("title", flat=True)
---
5. Related Model Queries
• Use select\_related and prefetch\_related to optimize related data access.
# Optimized: Single JOIN query for ForeignKey
books = Book.objects.select_related("author")
# For ManyToMany or reverse relations
authors = Author.objects.prefetch_related("book_set")
---
6. Raw SQL Queries (When Necessary)
books = Book.objects.raw("SELECT * FROM myapp_book WHERE pages > %s", [300])
for book in books:
print(book.title)---
7. Performance Tips
• Use only() or defer() to limit retrieved fields.
books = Book.objects.only("title")• Avoid chaining queries in loops.
• Use bulk\_create, bulk\_update for inserting/updating many records.
---
Summary
• Use aggregate(), annotate(), and Q objects for powerful filtering.
• Fetch only what you need using values, only, and select\_related.
• Optimize queries by reducing database hits and using Django’s ORM efficiently.
---
Exercise
• Write a Django query that returns all authors with more than 5 books, sorted by the number of books (descending). Then print their name and book count.
---
#Django #ORM #AdvancedQueries #QueryOptimization #WebDevelopment
https://t.me/DataScience4
❤2👍2
Topic: Django ORM – Transactions, Subqueries, and Custom Managers (Part 3)
---
1. Working with Transactions
• Django supports atomic transactions to ensure database integrity — either all operations succeed, or none do.
• Use atomic() as a decorator or context manager.
---
2. Subqueries and OuterRef
• Use Subquery and OuterRef to perform queries that depend on other queries.
---
3. Exists() and Conditional Logic
• Use Exists for optimized existence checks.
---
4. Custom Model Managers
• Add custom query logic to models via custom managers.
---
5. QuerySet Methods: Update, Delete, Bulk Operations
• update() modifies multiple records efficiently.
• delete() removes objects in bulk.
• bulk\_create() inserts many records at once.
---
6. Using Database Functions
• Django provides built-in SQL functions like Lower, Upper, Length, Concat, etc.
---
Summary
• Use transactions to maintain data integrity.
• Leverage subqueries, OuterRef, and Exists for complex logic.
• Create custom managers to encapsulate reusable query logic.
• Apply bulk operations and DB functions for performance and flexibility.
---
Exercise
• Create a custom manager for the
---
#Django #ORM #Transactions #Subqueries #CustomManagers #AdvancedDjango
https://t.me/DataScience4
---
1. Working with Transactions
• Django supports atomic transactions to ensure database integrity — either all operations succeed, or none do.
from django.db import transaction
@transaction.atomic
def create_author_and_book():
author = Author.objects.create(name="New Author")
Book.objects.create(title="New Book", author=author)
• Use atomic() as a decorator or context manager.
with transaction.atomic():
# multiple operations that must succeed together
...
---
2. Subqueries and OuterRef
• Use Subquery and OuterRef to perform queries that depend on other queries.
from django.db.models import Subquery, OuterRef
# Get latest book for each author
latest_books = Book.objects.filter(author=OuterRef('pk')).order_by('-published_date')
authors = Author.objects.annotate(latest_book=Subquery(latest_books.values('title')[:1]))
---
3. Exists() and Conditional Logic
• Use Exists for optimized existence checks.
from django.db.models import Exists
recent_books = Book.objects.filter(published_date__year=2023)
authors = Author.objects.annotate(has_recent_books=Exists(recent_books.filter(author=OuterRef('pk'))))
---
4. Custom Model Managers
• Add custom query logic to models via custom managers.
from django.db import models
class PublishedBookManager(models.Manager):
def get_queryset(self):
return super().get_queryset().filter(is_published=True)
class Book(models.Model):
title = models.CharField(max_length=200)
is_published = models.BooleanField(default=False)
objects = models.Manager() # Default manager
published = PublishedBookManager() # Custom manager
# Usage
Book.published.all()
---
5. QuerySet Methods: Update, Delete, Bulk Operations
• update() modifies multiple records efficiently.
Book.objects.filter(author__name="Alice").update(pages=300)
• delete() removes objects in bulk.
Book.objects.filter(published_date__year__lt=2000).delete()
• bulk\_create() inserts many records at once.
Book.objects.bulk_create([
Book(title="Book A", author=author),
Book(title="Book B", author=author),
])
---
6. Using Database Functions
• Django provides built-in SQL functions like Lower, Upper, Length, Concat, etc.
from django.db.models.functions import Upper
books = Book.objects.annotate(upper_title=Upper('title'))
---
Summary
• Use transactions to maintain data integrity.
• Leverage subqueries, OuterRef, and Exists for complex logic.
• Create custom managers to encapsulate reusable query logic.
• Apply bulk operations and DB functions for performance and flexibility.
---
Exercise
• Create a custom manager for the
Book model to return only books published in the last 5 years. Then use this manager in a view to list all recent books along with their authors.---
#Django #ORM #Transactions #Subqueries #CustomManagers #AdvancedDjango
https://t.me/DataScience4
❤5
Topic: Linked Lists in Python – Part 1: Introduction and Singly Linked List Basics
---
What is a Linked List?
• A linked list is a linear data structure where each element (called a node) contains:
• The data value.
• A pointer (or reference) to the next node.
• Unlike arrays, linked lists don’t require contiguous memory and can grow dynamically.
---
Why Use Linked Lists?
• Efficient insertions/deletions at the beginning or middle.
• No need for pre-defining size, unlike arrays.
• Used in memory-efficient applications like OS kernels, compilers, and real-time systems.
---
Types of Linked Lists
• Singly Linked List – Each node points to the next.
• Doubly Linked List – Nodes have next and previous pointers.
• Circular Linked List – The last node points back to the head.
---
Basic Structure of a Node
---
Building a Singly Linked List
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Traversing the List
Usage:
---
Inserting at the Beginning
---
Summary
• A singly linked list stores data as a sequence of nodes linked by references.
• Supports dynamic memory usage, fast insertions, and flexible resizing.
• The key is managing node connections safely and efficiently.
---
Exercise
• Implement a method
---
#DataStructures #LinkedList #DSA #Python #CodingBasics
https://t.me/DataScience4
---
What is a Linked List?
• A linked list is a linear data structure where each element (called a node) contains:
• The data value.
• A pointer (or reference) to the next node.
• Unlike arrays, linked lists don’t require contiguous memory and can grow dynamically.
---
Why Use Linked Lists?
• Efficient insertions/deletions at the beginning or middle.
• No need for pre-defining size, unlike arrays.
• Used in memory-efficient applications like OS kernels, compilers, and real-time systems.
---
Types of Linked Lists
• Singly Linked List – Each node points to the next.
• Doubly Linked List – Nodes have next and previous pointers.
• Circular Linked List – The last node points back to the head.
---
Basic Structure of a Node
class Node:
def __init__(self, data):
self.data = data
self.next = None
---
Building a Singly Linked List
class LinkedList:
def __init__(self):
self.head = None
def append(self, data):
new_node = Node(data)
if not self.head:
self.head = new_node
return
current = self.head
while current.next:
current = current.next
current.next = new_node
---
Traversing the List
def display(self):
current = self.head
while current:
print(current.data, end=" -> ")
current = current.next
print("None")
Usage:
ll = LinkedList()
ll.append(10)
ll.append(20)
ll.append(30)
ll.display() # Output: 10 -> 20 -> 30 -> None
---
Inserting at the Beginning
def insert_at_beginning(self, data):
new_node = Node(data)
new_node.next = self.head
self.head = new_node
---
Summary
• A singly linked list stores data as a sequence of nodes linked by references.
• Supports dynamic memory usage, fast insertions, and flexible resizing.
• The key is managing node connections safely and efficiently.
---
Exercise
• Implement a method
length() that returns the number of nodes in the list.---
#DataStructures #LinkedList #DSA #Python #CodingBasics
https://t.me/DataScience4
❤3
Topic: Linked Lists in Python – Part 2: Insertion, Deletion, and Search Operations
---
Recap from Part 1
• A singly linked list consists of nodes, where each node holds data and a pointer to the next node.
• We've implemented basic append and display functions.
Now we’ll explore insertion at specific positions, deletion, and searching.
---
1. Insert at a Specific Position
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2. Delete a Node by Value
---
3. Delete a Node by Index
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4. Search for an Element
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5. Complete Class with All Methods
*(You can reuse the method definitions above.)*
---
Summary
• You can manipulate linked lists with insertions and deletions at any position.
• Searching through a singly linked list is O(n).
• Always check for edge cases: empty list, index bounds, and duplicates.
---
Exercise
• Write a method
---
#DSA #LinkedList #Python #Insertion #Deletion #Search
https://t.me/DataScience4
---
Recap from Part 1
• A singly linked list consists of nodes, where each node holds data and a pointer to the next node.
• We've implemented basic append and display functions.
Now we’ll explore insertion at specific positions, deletion, and searching.
---
1. Insert at a Specific Position
def insert_at_position(self, index, data):
if index < 0:
raise IndexError("Index cannot be negative")
new_node = Node(data)
if index == 0:
new_node.next = self.head
self.head = new_node
return
current = self.head
for _ in range(index - 1):
if not current:
raise IndexError("Index out of bounds")
current = current.next
new_node.next = current.next
current.next = new_node
---
2. Delete a Node by Value
def delete_by_value(self, value):
if not self.head:
return
if self.head.data == value:
self.head = self.head.next
return
current = self.head
while current.next and current.next.data != value:
current = current.next
if current.next:
current.next = current.next.next
---
3. Delete a Node by Index
def delete_by_index(self, index):
if index < 0:
raise IndexError("Index cannot be negative")
if not self.head:
raise IndexError("List is empty")
if index == 0:
self.head = self.head.next
return
current = self.head
for _ in range(index - 1):
if not current.next:
raise IndexError("Index out of bounds")
current = current.next
if current.next:
current.next = current.next.next
---
4. Search for an Element
def search(self, value):
current = self.head
index = 0
while current:
if current.data == value:
return index
current = current.next
index += 1
return -1 # Not found
---
5. Complete Class with All Methods
class LinkedList:
def __init__(self):
self.head = None
def append(self, data): ...
def display(self): ...
def insert_at_position(self, index, data): ...
def delete_by_value(self, value): ...
def delete_by_index(self, index): ...
def search(self, value): ...
*(You can reuse the method definitions above.)*
---
Summary
• You can manipulate linked lists with insertions and deletions at any position.
• Searching through a singly linked list is O(n).
• Always check for edge cases: empty list, index bounds, and duplicates.
---
Exercise
• Write a method
reverse() that reverses the linked list in-place and test it on a list of 5+ elements.---
#DSA #LinkedList #Python #Insertion #Deletion #Search
https://t.me/DataScience4
❤2
Topic: Linked Lists in Python – Part 3: Reversing, Detecting Loops, and Middle Node
---
In this part, we’ll explore advanced operations that are frequently asked in coding interviews using singly linked lists.
---
1. Reverse a Linked List (Iterative)
• Time Complexity: O(n)
• Space Complexity: O(1)
---
2. Find the Middle of the Linked List
• Use the slow and fast pointer approach.
---
3. Detect a Loop in the Linked List
• Use Floyd’s Cycle Detection Algorithm (a.k.a. Tortoise and Hare).
---
4. Find the N-th Node from the End
---
5. Full Example: Testing All Methods
---
Summary
• Use pointer manipulation for efficient algorithms in linked lists.
• Common techniques:
• Fast/slow pointers
• Reversal by in-place re-linking
• Two-pointer gap approach for nth from end
---
Exercise
• Write a method
---
#DSA #LinkedList #ReverseList #LoopDetection #TwoPointerTechnique
https://t.me/DataScience4
---
In this part, we’ll explore advanced operations that are frequently asked in coding interviews using singly linked lists.
---
1. Reverse a Linked List (Iterative)
def reverse(self):
prev = None
current = self.head
while current:
next_node = current.next
current.next = prev
prev = current
current = next_node
self.head = prev
• Time Complexity: O(n)
• Space Complexity: O(1)
---
2. Find the Middle of the Linked List
• Use the slow and fast pointer approach.
def find_middle(self):
slow = fast = self.head
while fast and fast.next:
slow = slow.next
fast = fast.next.next
return slow.data if slow else None
---
3. Detect a Loop in the Linked List
• Use Floyd’s Cycle Detection Algorithm (a.k.a. Tortoise and Hare).
def has_loop(self):
slow = fast = self.head
while fast and fast.next:
slow = slow.next
fast = fast.next.next
if slow == fast:
return True
return False
---
4. Find the N-th Node from the End
def nth_from_end(self, n):
first = self.head
second = self.head
for _ in range(n):
if not first:
return None
first = first.next
while first:
first = first.next
second = second.next
return second.data
---
5. Full Example: Testing All Methods
ll = LinkedList()
for value in [10, 20, 30, 40, 50]:
ll.append(value)
ll.display()
ll.reverse()
ll.display()
print("Middle:", ll.find_middle())
print("Has Loop?", ll.has_loop())
print("3rd from End:", ll.nth_from_end(3))
---
Summary
• Use pointer manipulation for efficient algorithms in linked lists.
• Common techniques:
• Fast/slow pointers
• Reversal by in-place re-linking
• Two-pointer gap approach for nth from end
---
Exercise
• Write a method
is_palindrome() that checks if the linked list reads the same forwards and backwards (without converting it to a list or using extra space).---
#DSA #LinkedList #ReverseList #LoopDetection #TwoPointerTechnique
https://t.me/DataScience4
❤5
Topic: Linked Lists in Python – Part 4: Merging, Sorting, and Advanced Interview Problems
---
In this final part of the Linked List series, we’ll tackle more advanced and practical use cases like merging sorted lists, sorting a linked list, and interview-level challenges.
---
1. Merging Two Sorted Linked Lists
---
2. Sorting a Linked List (Merge Sort – O(n log n))
• Attach this to your
---
3. Removing Duplicates from a Sorted List
---
4. Intersection Point of Two Linked Lists
---
5. Flatten a Multilevel Linked List
Imagine a list where each node has
---
Summary
• You now know how to merge, sort, and deduplicate linked lists.
• Techniques like merge sort, two-pointer traversal, and recursive flattening are essential for mastering linked lists.
• These problems are frequently asked in interviews at top tech companies.
---
Exercise
• Given two unsorted linked lists, write a function that returns a new linked list containing only the elements present in both lists (intersection), without using extra space or sets.
---
#DSA #LinkedList #MergeSort #AdvancedDSA #CodingInterview
https://t.me/DataScience4
---
In this final part of the Linked List series, we’ll tackle more advanced and practical use cases like merging sorted lists, sorting a linked list, and interview-level challenges.
---
1. Merging Two Sorted Linked Lists
def merge_sorted_lists(l1, l2):
dummy = Node(0)
tail = dummy
while l1 and l2:
if l1.data < l2.data:
tail.next = l1
l1 = l1.next
else:
tail.next = l2
l2 = l2.next
tail = tail.next
tail.next = l1 or l2
return dummy.next
---
2. Sorting a Linked List (Merge Sort – O(n log n))
def merge_sort(head):
if not head or not head.next:
return head
# Split list
slow, fast = head, head.next
while fast and fast.next:
slow = slow.next
fast = fast.next.next
mid = slow.next
slow.next = None
left = merge_sort(head)
right = merge_sort(mid)
return merge_sorted_lists(left, right)
• Attach this to your
LinkedList class to sort self.head.---
3. Removing Duplicates from a Sorted List
def remove_duplicates(self):
current = self.head
while current and current.next:
if current.data == current.next.data:
current.next = current.next.next
else:
current = current.next
---
4. Intersection Point of Two Linked Lists
def get_intersection_node(headA, headB):
if not headA or not headB:
return None
a, b = headA, headB
while a != b:
a = a.next if a else headB
b = b.next if b else headA
return a # Can be None or the intersecting node
---
5. Flatten a Multilevel Linked List
Imagine a list where each node has
next and child pointers. Recursively flatten:def flatten(node):
if not node:
return None
next_node = node.next
if node.child:
child_tail = flatten(node.child)
node.next = node.child
node.child = None
child_tail.next = flatten(next_node)
return child_tail if child_tail.next else child_tail
else:
node.next = flatten(next_node)
return node
---
Summary
• You now know how to merge, sort, and deduplicate linked lists.
• Techniques like merge sort, two-pointer traversal, and recursive flattening are essential for mastering linked lists.
• These problems are frequently asked in interviews at top tech companies.
---
Exercise
• Given two unsorted linked lists, write a function that returns a new linked list containing only the elements present in both lists (intersection), without using extra space or sets.
---
#DSA #LinkedList #MergeSort #AdvancedDSA #CodingInterview
https://t.me/DataScience4
❤2