codeverra

DSA with Python: Zero to Hero

Mon, 01 Jan 0001 00:00:00 +0000

A beginner-first, structured course to learn Python and Data Structures from scratch.

DSA Live Practice Series

Mon, 01 Jan 0001 00:00:00 +0000

Daily live problem-solving sessions to build consistency in DSA.

Advanced LLD Topics: A Deep Dive

Fri, 04 Sep 2026 00:00:00 +0000

Advanced low-level design topics for real systems, interviews, and production code: building on SOLID and design patterns.

Design Patterns, Part 1: Foundations and Creational Patterns

Fri, 04 Sep 2026 00:00:00 +0000

Foundations of the GoF design pattern catalogue and creational patterns: Singleton, Factory, Builder, Prototype, and Abstract Factory.

Design Patterns, Part 2: Structural Patterns

Fri, 04 Sep 2026 00:00:00 +0000

Structural design patterns: how to combine classes and objects into larger structures that stay flexible and maintainable.

Design Patterns, Part 3: Behavioral Patterns

Fri, 04 Sep 2026 00:00:00 +0000

Behavioral design patterns: how objects communicate, divide responsibility, and coordinate behavior in complex systems.

Design Patterns: Practice Workbook

Fri, 04 Sep 2026 00:00:00 +0000

Hands-on design pattern practice problems to prove you understand creational, structural, and behavioral patterns.

LLD Foundations - SOLID Principles

Fri, 04 Sep 2026 00:00:00 +0000

A complete guide to solid principles which are fundamental of object oriented design.

Object-Oriented Programming in Python: A Deep Dive

Fri, 04 Sep 2026 00:00:00 +0000

A complete guide to Python OOP: why it exists, what problems it solves, and how to wield it well in real systems.

SOLID Principles: A Complete Deep Dive

Fri, 04 Sep 2026 00:00:00 +0000

A rigorous treatment of the five SOLID principles: formal statements, worked examples, tradeoffs, and when not to apply them.

SOLID Principles: A Complete Deep Dive

Fri, 04 Sep 2026 00:00:00 +0000

A rigorous treatment of the five SOLID principles: formal statements, worked examples, tradeoffs, and when not to apply them.

UML Deep Dive: Class Diagrams and Sequence Diagrams

Fri, 04 Sep 2026 00:00:00 +0000

A standardized visual language for communicating class structures and runtime interactions: class diagrams and sequence diagrams explained.

Array Patterns - The Complete Study Guide

Sat, 21 Mar 2026 00:00:00 +0000

A complete index of the most important array problem-solving patterns for DSA, with links to each pattern guide.

Arrays in Python - Complete Guide

Sat, 21 Mar 2026 00:00:00 +0000

Everything you need to know about arrays and lists in Python for DSA - operations, patterns, and common problems.

Binary Search Pattern - Complete Guide

Sat, 21 Mar 2026 00:00:00 +0000

Understand binary search as a pattern beyond sorted arrays - templates, variations, and common problems.

Complexity Analysis - Time and Space

Sat, 21 Mar 2026 00:00:00 +0000

Understand Big O notation, time complexity, and space complexity with clear examples in Python.

Control Flow in Python

Sat, 21 Mar 2026 00:00:00 +0000

Control Flow in Python

Making Decisions in Your Code – if, elif, else, and Beyond

Before We Begin – Why Control Flow is Everything

Every program you have ever used makes decisions.

When you log into a website: if the password is correct, show the dashboard, otherwise show an error. When your food delivery app calculates the delivery fee: if the order is above Rs.200, delivery is free, else charge Rs.30. When a data pipeline processes records: if the record is valid, process it, else log an error and skip it.

HashMap and Frequency Counting Pattern - Complete Guide

Sat, 21 Mar 2026 00:00:00 +0000

Learn how to use hashmaps and frequency counting to solve common DSA problems efficiently in Python.

Linked Lists in Python - Complete Guide

Sat, 21 Mar 2026 00:00:00 +0000

Understand linked lists from scratch - nodes, pointers, singly and doubly linked lists with Python implementations.

Logging and System Interaction in Python

Sat, 21 Mar 2026 00:00:00 +0000

Logging and System Interaction in Python

Professional Observability with the logging Module and the os Module

Before We Begin – Why This Matters More Than It Looks

Here is a situation every developer eventually faces.

You write a script that processes data overnight. It runs on a server while you sleep. In the morning you check the output and something is wrong. Half the records are missing. You have no idea what happened because your script used print() for all its messages and those prints went nowhere – there was nobody watching the terminal.

Modules, Packages, and the Python Ecosystem

Sat, 21 Mar 2026 00:00:00 +0000

Understand how Python modules and packages work, how to create your own, and how to navigate the Python ecosystem.

Object-Oriented Programming in Python - Masterclass

Sat, 21 Mar 2026 00:00:00 +0000

A comprehensive guide to OOP in Python - classes, objects, inheritance, encapsulation, and polymorphism.

OOP Practice - Problems and Solutions

Sat, 21 Mar 2026 00:00:00 +0000

Object-Oriented Programming – Assignment

Four Real-World Problems to Solve Using OOP

This assignment covers OOP Basics and Intermediate concepts. For each problem, read the description carefully, understand what the system needs to do, and design your classes before writing any code. Planning on paper first is not optional – it is part of the exercise.

How to Approach Each Problem

Before writing a single line of code for any problem:

Prefix Sum Pattern - Complete Guide

Sat, 21 Mar 2026 00:00:00 +0000

Master the prefix sum technique for range query problems with Python examples and practice problems.

Python Basics Masterclass

Sat, 21 Mar 2026 00:00:00 +0000

A complete beginner-friendly guide to Python basics - syntax, data types, variables, and core concepts.

Python Collections - Theory

Sat, 21 Mar 2026 00:00:00 +0000

Python Collections

Lists, Tuples, Dictionaries, and Sets – The Four Ways to Store Data

Before We Begin – Why Collections Are Central to Everything

At some point you stop writing programs that work on one value at a time and start writing programs that work on many values at once. A list of students. A dictionary of city populations. A set of unique tags. A tuple representing a coordinate.

Collections are the bridge between “I know Python basics” and “I can solve real problems.” Everything that follows in this curriculum – loops, functions, Pandas, APIs – assumes you are comfortable with collections.

Python Learning Roadmap

Sat, 21 Mar 2026 00:00:00 +0000

A structured roadmap to learning Python from scratch to advanced - what to learn, in what order, and why.

Python Loops Masterclass

Sat, 21 Mar 2026 00:00:00 +0000

🔁 Python Loops Masterclass

Complete Command Over for and while Loops — From Basics to Patterns

Who is this for? You know Python basics — variables, conditionals, functions. Now you want to truly master loops — not just use them, but think in them. This guide covers every loop concept in Python, with simple examples before every idea.

📌 Table of Contents

Why Loops Exist
The for Loop
Iterating Over Different Data Types
The range() Function
The while Loop
break — Exit the Loop Early
continue — Skip to the Next Iteration
pass — Do Nothing (Placeholder)
else with Loops
enumerate() — Loop with an Index
zip() — Loop Over Multiple Sequences
Nested Loops
List Comprehensions
Dictionary and Set Comprehensions
Loop Patterns Every Programmer Uses
Common Loop Mistakes and How to Avoid Them
Practice Questions
What We Covered + What’s Next

1. Why Loops Exist

Imagine you need to print a welcome message for 500 students. Without loops:

Python Refresher for DSA

Sat, 21 Mar 2026 00:00:00 +0000

A quick refresher on the Python concepts you need before diving into Data Structures and Algorithms.

Regular Expressions in Python

Sat, 21 Mar 2026 00:00:00 +0000

Regular Expressions in Python

Pattern Matching, Text Processing, and the re Module

Before We Begin – Why Regular Expressions Matter

Here is a real problem. You have a CSV file with 50,000 rows of customer data. The phone number column is a mess:

+91-9876543210
9876 543 210
(091) 9876-543210
91-98765-43210
9876543210
+919876543210

All of these are the same phone number in different formats. You need to extract just the 10-digit number from all of them.

Sliding Window Pattern - Complete Guide

Sat, 21 Mar 2026 00:00:00 +0000

Learn the sliding window technique to efficiently solve subarray and substring problems in Python.

Stacks in Python - Complete Guide

Sat, 21 Mar 2026 00:00:00 +0000

Learn how stacks work, how to implement them in Python, and how to solve common stack-based problems.

Strings in Python - Complete Guide

Sat, 21 Mar 2026 00:00:00 +0000

A practical guide to string operations and manipulation in Python for DSA problem solving.

The Complete DSA with Python - Master Roadmap

Sat, 21 Mar 2026 00:00:00 +0000

A structured roadmap to mastering Data Structures and Algorithms using Python, from basics to advanced topics.

Two Pointers Pattern - Complete Guide

Sat, 21 Mar 2026 00:00:00 +0000

Master the two pointers technique with clear explanations, Python implementations, and practice problems.

Type Hints in Python

Sat, 21 Mar 2026 00:00:00 +0000

Type Hints in Python

Writing Code That Explains Itself – The typing Module and Beyond

Before We Begin – Why Type Hints Matter

Here is a function:

def calculate_discount(price, discount, is_member):
 ...

What type is price? A float? An int? A string like "1299"? What is discount? A percentage like 18.5? Or a multiplier like 0.185? What does is_member do to the result?

You cannot tell without reading the implementation. In a codebase with hundreds of functions, this adds up to an enormous cognitive load.

What is DSA and Why Do We Learn It

Sat, 21 Mar 2026 00:00:00 +0000

A clear introduction to Data Structures and Algorithms - what they are, why they matter, and how to approach learning them.

Working with the Real World in Python

Sat, 21 Mar 2026 00:00:00 +0000

Learn how Python interacts with real-world systems - APIs, files, databases, and external libraries.

Complete Guide to Numpy Library in Python

Wed, 18 Mar 2026 00:00:00 +0000

Complete practice session on Numpy in python

Complete Guide to Pandas in Python

Wed, 18 Mar 2026 00:00:00 +0000

Complete practice session on Pandas in python

Master Collections in Python

Wed, 18 Mar 2026 00:00:00 +0000

Complete practice session on collections in python

Master Loops in Python

Wed, 18 Mar 2026 00:00:00 +0000

Complete practice session on Loops in python

Numpy Masterclass - Beginner to Advanced

Wed, 18 Mar 2026 00:00:00 +0000

Get a comprehensive introduction to Numpy library in python

Pandas Masterclass - Beginner to Advanced

Wed, 18 Mar 2026 00:00:00 +0000

Get a comprehensive introduction to pandas library in python

Exception Handling in Python - Complete Guide

Tue, 17 Mar 2026 00:00:00 +0000

Learn about try-except-finally and custom exceptions in Python

File Handling in Python - Complete Guide

Tue, 17 Mar 2026 00:00:00 +0000

Learn about working with files in Python

Filtering and Querying data

Tue, 17 Mar 2026 00:00:00 +0000

Learn about WHERE, GROUPBY and other important commands

Functions in Python - Complete Guide

Tue, 17 Mar 2026 00:00:00 +0000

Learn everything about writing fcuntions in Python

Group by and Aggregations

Tue, 17 Mar 2026 00:00:00 +0000

Learn about grouping and aggregating on tables

Higher Order Functions and Decorators in Python

Tue, 17 Mar 2026 00:00:00 +0000

Learn about higher order functions like map, filter, reduce and decorators

Indexes and Schema Design

Tue, 17 Mar 2026 00:00:00 +0000

Learn about using and creating indexes on tabels to improve query performance

Introduction to SQL and Databases

Tue, 17 Mar 2026 00:00:00 +0000

Introduction to PostgreSQl and writing queries using pgAdmin tool

Iterators and Generators in Python - Complete Guide

Tue, 17 Mar 2026 00:00:00 +0000

Learn about iterables and iterators and generators in python

Itertools Module in Python - Complete Guide

Tue, 17 Mar 2026 00:00:00 +0000

Learn about the very useful itertools library in python

Joins and Relationships

Tue, 17 Mar 2026 00:00:00 +0000

Learn about different types of joins

Joins and Relationships

Tue, 17 Mar 2026 00:00:00 +0000

Learn about different types of joins

Modifying data & Schema Changes

Tue, 17 Mar 2026 00:00:00 +0000

Learn about making changes to the existing tables

Practice Pandas on IPL Dataset

Tue, 17 Mar 2026 00:00:00 +0000

Master data analysis in Python using the pandas library using hands on practice on IPL dataset

Practice Pandas on Titanic Dataset

Tue, 17 Mar 2026 00:00:00 +0000

Master data analysis in Python using the pandas library using hands on practice on Titanic dataset

Practice Pandas on Zomato Dataset

Tue, 17 Mar 2026 00:00:00 +0000

Master data analysis in Python using the pandas library using hands on practice on Zomato dataset

SQL Practice on Cricket Dataset: 12 Questions with Solutions

Tue, 17 Mar 2026 00:00:00 +0000

Pratice easy, medium and hard questions on cricket dataset.

SQL Practice on Shopping Dataset: SQL Questions with Solutions

Tue, 17 Mar 2026 00:00:00 +0000

Pratice easy, medium and hard questions on cricket dataset.

A Practical DSA Learning Roadmap

Tue, 30 Dec 2025 00:00:00 +0000

A structured roadmap to learn Data Structures and Algorithms the right way and why it matters beyond interview preparation

Analysis of Time Complexity Explained with Python Examples

Tue, 30 Dec 2025 00:00:00 +0000

A beginner-friendly and practical guide to understanding time complexity with clear explanations and Python examples written as plain text.

Array Patterns for Problem Solving

Tue, 30 Dec 2025 00:00:00 +0000

A structured guide to common array problem-solving patterns, helping you identify the right approach instead of memorizing solutions.

BFS vs DFS Explained Clearly

Tue, 30 Dec 2025 00:00:00 +0000

A detailed and conceptual explanation of Breadth-First Search (BFS) and Depth-First Search (DFS), covering their working principles, differences, complexities, and real-world applications.

Binary Search Explained Clearly

Tue, 30 Dec 2025 00:00:00 +0000

A clear and structured explanation of binary search, including how it works, requirements, examples, complexities, and interview insights.

Complete Python Programming Syllabus (Beginner to Advanced)

Tue, 30 Dec 2025 00:00:00 +0000

A structured Python programming roadmap from zero to professional level, covering fundamentals, core concepts, advanced topics, and real-world applications.

Concept of Dynamic Programming Explained Clearly

Tue, 30 Dec 2025 00:00:00 +0000

A clear and conceptual explanation of Dynamic Programming, focusing on overlapping subproblems and optimal substructure with intuitive examples.

Different Sorting Algorithms Explained Clearly

Tue, 30 Dec 2025 00:00:00 +0000

A structured and easy-to-understand explanation of major sorting algorithms, their working ideas, time and space complexities, and real-world usage.

DSA With Python - Zero to Hero (Curriculum)

Tue, 30 Dec 2025 00:00:00 +0000

Learn Python programming along with Data Structures and Algorithms from scratch and become a hero in the field."

Recursion Explained from Basics

Tue, 30 Dec 2025 00:00:00 +0000

A clear and beginner-friendly explanation of recursion, covering how it works, its components, types, advantages, disadvantages, and use cases.

Searching in Arrays (Sorted and Unsorted)

Tue, 30 Dec 2025 00:00:00 +0000

A clear and practical guide to searching techniques in arrays, explaining linear search and binary search with concepts, complexities, and real-world use cases.

Mon, 01 Jan 0001 00:00:00 +0000

Low-Level Design Interview Questions — A Complete Walkthrough

Who this is for: Anyone preparing for low-level design interviews — or anyone who wants to see the OOP, SOLID, and design-pattern concepts from the previous documents come together into real, working designs. We’ll walk through six classic problems end-to-end.

How to Approach Any LLD Interview Problem
The Universal Framework
Common Pitfalls in LLD Interviews
Problem 1 — Design a Parking Lot
Problem 2 — Design an Elevator System
Problem 3 — Design a Library Management System
Problem 4 — Design a Vending Machine
Problem 5 — Design a Splitwise-Like Expense Sharing System
Problem 6 — Design a Ride-Hailing System (Uber-Lite)
Meta-Patterns Across All Six Problems
Final Interview Tips

1. How to Approach Any LLD Interview Problem

The LLD interview isn’t really about the specific problem — parking lot, elevator, chess, whatever. It’s about demonstrating a structured thinking process. The interviewer watches how you decompose ambiguity, handle tradeoffs, and communicate design decisions.

Mon, 01 Jan 0001 00:00:00 +0000

LLD Deep Dive #1 — Designing a Parking Lot

What this document is: A genuine, step-by-step walkthrough of how to think through a Parking Lot LLD problem in an interview. Not a finished design dropped on you — but the reasoning, the false starts, the alternatives weighed, and the justifications that lead to each design decision.

Time investment: Read this slowly. If you’re doing this for interview prep, it’s worth treating each section as its own thinking exercise — pause and ask yourself “what would I do here?” before reading on.

Mon, 01 Jan 0001 00:00:00 +0000

LLD Deep Dive #2 — Designing an Elevator System

What this document is: A genuine, step-by-step walkthrough of how to think through an Elevator LLD problem in an interview. We’ll reason from first principles, weigh alternatives, and document each design decision — building toward a clean, extensible design centered on the State pattern.

Why This Problem Matters
Stage 1 — Receiving the Problem
Stage 2 — Clarifying Requirements
Stage 3 — Identifying Entities
Stage 4 — Modeling Requests (Internal vs External)
Stage 5 — The State Pattern Decision
Stage 6 — Implementing the States
Stage 7 — The Elevator Class
Stage 8 — The Dispatcher and Scheduling Strategy
Stage 9 — The Building (Top-Level Coordinator)
Stage 10 — Validating with a Mental Walkthrough
Stage 11 — Anticipating Follow-Up Questions
Final Reflection — What This Problem Teaches

1. Why This Problem Matters

If Parking Lot is the canonical “model relationships” problem, Elevator is the canonical “model state transitions” problem. It’s specifically designed (whether interviewers know it or not) to make the State pattern shine.

Mon, 01 Jan 0001 00:00:00 +0000

LLD Deep Dive #3 — Designing a Library Management System

What this document is: A genuine, step-by-step walkthrough of how to think through a Library Management LLD problem. We’ll reason from first principles, weigh alternatives, and document each design decision — building toward a clean, extensible system that handles books, members, loans, fines, and reservations.

Why This Problem Matters
Stage 1 — Receiving the Problem
Stage 2 — Clarifying Requirements
Stage 3 — Identifying Entities (And the Big Modeling Decision)
Stage 4 — Modeling Books vs Book Copies
Stage 5 — Modeling Members and Their Policies
Stage 6 — The Loan Lifecycle
Stage 7 — The Reservation Queue
Stage 8 — Search Functionality
Stage 9 — The Library (Top-Level Coordinator)
Stage 10 — Validating with a Mental Walkthrough
Stage 11 — Anticipating Follow-Up Questions
Final Reflection — What This Problem Teaches

1. Why This Problem Matters

The library system is the canonical “policy-driven domain modeling” interview problem. What it tests:

Mon, 01 Jan 0001 00:00:00 +0000

LLD Deep Dive #4: Designing a Tic Tac Toe Game

What this document covers: A rigorous, step-by-step examination of how to approach a Tic Tac Toe Low-Level Design (LLD) problem in a technical interview. The document walks through the reasoning process at each design juncture, evaluates competing alternatives, and provides justification for every decision made. The finished design is a consequence of the reasoning, not its starting point.

How to read this document: Read it slowly and deliberately. The problem appears trivial at the surface, since Tic Tac Toe requires only a three by three grid, two players, and a rule for detecting three marks in a row. That surface simplicity is precisely why the problem is used in interviews: it invites the unwary candidate to produce a short procedural script, when the actual expectation is a properly modelled, extensible, and testable object-oriented design.

Mon, 01 Jan 0001 00:00:00 +0000

LLD Deep Dive #4: Designing a Grocery / E-Commerce Management System

What this document is: A step-by-step walkthrough of the reasoning process required to design an e-commerce LLD problem in an interview setting. The specific flavour is a grocery store, though the design generalises to any online retail system. Every design decision is derived from first principles, alternatives are evaluated at each fork, and the resulting system is one whose components can be explained, defended, and extended.

Mon, 01 Jan 0001 00:00:00 +0000

What this document is. This is a comprehensive, first-principles walkthrough of how to design a ride-sharing system (of the Uber or Ola variety) as a low-level design (LLD) interview problem. It reasons from the vague problem statement through requirement clarification, entity identification, class hierarchy decisions, behavioural modelling with design patterns, and finally a fully composed system. Every design choice is stated together with the alternatives that were considered and the criteria that decided between them, so that a learner reading this can not only reproduce the design but also defend it and adapt it.

Mon, 01 Jan 0001 00:00:00 +0000

LLD Deep Dive #4: Designing an ATM System

What this document is: A structured, step-by-step walkthrough of the ATM low-level design problem as it would be reasoned through in a technical interview. The document proceeds from first principles, weighs alternative designs at each decision point, and arrives at a solution that combines the State pattern, the Strategy pattern, the Command pattern, and a clean separation between hardware and software concerns. Definitions of every technical term are provided when the term is introduced, so the document can be read without prior familiarity with the design-pattern literature.

Mon, 01 Jan 0001 00:00:00 +0000

LLD Deep Dive #4: Designing a Movie Ticket Booking System (BookMyShow-style)

Purpose of this document. A staged walkthrough of how to reason through a Movie Ticket Booking Low-Level Design (LLD) problem in an interview setting. Each design decision is presented alongside the alternatives that were considered and the rationale for the final choice. The resulting design is modular, extensible, and treats concurrency as a first-class concern rather than a post-hoc extension.

Mon, 01 Jan 0001 00:00:00 +0000

LLD Deep Dive #4 — Designing a Text Editor

What this document is: A genuine, step-by-step walkthrough of how to think through a Text Editor LLD problem in an interview. Not a finished design dropped on you — but the reasoning, the false starts, the alternatives weighed, and the justifications behind each design decision.

Time investment: Read this slowly. If you’re doing this for interview prep, treat each stage as its own thinking exercise — pause and ask yourself “what would I do here?” before reading on.

Mon, 01 Jan 0001 00:00:00 +0000

What this document is. This is a complete, step by step walkthrough of how to design an expense sharing system of the kind popularised by the Splitwise application. It reasons from first principles, states the alternatives at every decision point, and justifies the option that is chosen. The design developed here is implemented as a small, runnable, modular Python project that accompanies this document, so that every concept discussed in prose can be examined and executed as real code.

Mon, 01 Jan 0001 00:00:00 +0000

Python: Where to Start and Where It Can Take You | Codeverra

Lecture 01 / Python Fundamentals

Python: Where to Start
and Where It Can Take You

A complete introduction to why Python matters, how to set it up, the basics of its syntax, and an honest roadmap of everything that lies ahead for you.