DEV Community: Harish raj

day 2 python

Harish raj — Mon, 26 Oct 2026 19:54:43 +0000

Introduction
Today, I learned about Python identifiers, variables, reserved keywords, built-in functions, data types, and ASCII. These are the fundamental concepts of Python programming that help us write and understand programs effectively.

Variables and Identifiers in Python A variable is a name used to refer to a value in a program. In Python, a variable is created when we assign a value to a name.

An identifier is the name used to identify a variable, function, class, or another programming object.

Syntax:

name = "Harish"
age = 23
Here:

name and age are identifiers.

"Harish" and 23 are values.

= is the assignment operator.

The assignment operator assigns the value on the right-hand side to the name on the left-hand side.

Python variables are dynamically typed, which means we do not need to declare their data types explicitly.

Rules for Naming Identifiers Python identifiers must follow specific naming rules.

They can contain uppercase letters (A–Z) and lowercase letters (a–z).

They can contain digits (0–9), but cannot start with a digit.

They can contain underscores (_).

They cannot contain spaces or special characters such as @, #, and $.

They cannot be Python reserved keywords.

Python is case-sensitive, so name, Name, and NAME are different identifiers.

Examples:

name = "Harish" # Valid
Name = "Raj" # Valid
user_name = "Harish" # Valid
age2 = 23 # Valid

2name = "Harish" # Invalid

user-name = "Raj" # Invalid

class = "Python" # Invalid

Types of Naming Conventions Python uses underscores in different naming conventions to communicate the intended use of an identifier.

name = "Harish"
name = "Harish"
__name = "Harish"
__name_ = "Harish"
name – A normal public-style name.

_name – A convention indicating that the name is intended for internal use.

__name – Inside a class, a leading double underscore triggers name mangling, which helps avoid naming conflicts with subclasses. It is not a strict privacy mechanism.

name – A name surrounded by double underscores is commonly reserved for special Python methods and attributes, such as init.

These naming conventions help developers communicate how identifiers are intended to be used.

Reserved Keywords in Python Reserved keywords are words that have special meanings in Python's syntax. They cannot be used as ordinary identifiers, such as variable names.

Examples include:

if, else, for, while, def, class, return, import, True, and False.

For example:

if = 10 # SyntaxError
The word if is reserved for conditional statements, so it cannot be used as a variable name.

How to Display Python Keywords
Python provides the built-in keyword module to identify reserved keywords.

import keyword

print(keyword.kwlist)
print(len(keyword.kwlist))
import keyword imports the keyword module.

keyword.kwlist returns a list of Python keywords.

len(keyword.kwlist) counts the keywords in that list.

print() displays the results.

In Python 3.13, there are 35 hard keywords. The count can vary by Python version, and soft keywords are handled separately.

Built-in Functions in Python A built-in function is a function provided by Python that we can use without defining it ourselves or importing a module.

Examples include:

print() – Displays output.

len() – Returns the length of an object.

type() – Returns the type of an object.

input() – Reads user input.

int() – Converts a compatible value to an integer.

Example:

name = "Python"

print(name)
print(len(name))
print(type(name))
Output:

Python
6

Here, print(), len(), and type() are built-in functions.

What Is an IDE? IDE stands for Integrated Development Environment. It is a software application that provides tools for writing, running, debugging, and managing code.

Examples of Python development environments include:

Visual Studio Code

PyCharm

IDLE

JupyterLab

An IDE or code editor helps developers write programs more efficiently.

Basic Data Types in Python Python provides different data types to represent different kinds of values.

Data type Description Example
int Whole numbers age = 23
float Decimal numbers price = 99.5
str Text name = "Python"
bool Boolean values is_valid = True
Integer
An integer represents a whole number without a decimal point.

age = 23
print(type(age))
Float
A float represents a number with a fractional or decimal component.

price = 99.5
print(type(price))
String
A string represents text enclosed in single or double quotation marks.

language = "Python"
print(type(language))
Boolean
A Boolean represents one of two logical values: True or False.

is_student = True
print(type(is_student))
Boolean values are not the same as the integers 1 and 0, although Python allows certain numeric operations between them.

What Is ASCII? ASCII stands for American Standard Code for Information Interchange. It is a character-encoding standard that assigns numerical codes to English letters, digits, punctuation marks, and certain control characters.

For example:

A = 65

a = 97

0 = 48

Python can display the Unicode code point of a character using the ord() function.

print(ord("A"))
print(ord("a"))
print(ord("0"))
Output:

65
97
48
ASCII is a subset of Unicode. Python strings support Unicode, so Python can represent characters from many languages beyond the original ASCII character set.

Conclusion
Today, I learned the basics of Python identifiers, variable assignment, naming conventions, reserved keywords, built-in functions, IDEs, data types, and ASCII. These concepts form the foundation for writing Python programs and understanding how data is represented and processed.

By practising these fundamentals, I can build a stronger foundation for advanced Python topics such as functions, loops, object-oriented programming, data analysis, and artificial intelligence.

python day 1

Harish raj — Mon, 26 Oct 2026 17:57:53 +0000

Introduction
Python is a powerful, high-level, general-purpose programming language known for its simple syntax, readability, and versatility. It is widely used in data science, data analysis, machine learning, artificial intelligence (AI), web development, networking, automation, scripting, and game development.

Python helps developers write code with fewer lines, making it easier to learn, understand, and maintain.

Applications of Python Python is used in many areas of software development.

Data Science and Data Analysis: Python helps collect, process, analyze, and visualize data using libraries such as Pandas, NumPy, and Matplotlib.

Machine Learning and AI: Python is widely used to develop machine learning models and AI applications with libraries such as Scikit-learn, TensorFlow, and PyTorch.

Web Development: Python supports web application development using frameworks such as Django and Flask.

Database Applications: Python can connect to databases such as MySQL, PostgreSQL, and SQLite to store, retrieve, and manage information.

Networking: Python can be used to develop network tools, communicate between computers, and work with network protocols.

Scripting and Automation: Python helps automate repetitive tasks, manage files, and execute system operations.

Game Development: Python can be used to create games using libraries and frameworks such as Pygame.

Python Implementations Python has different implementations that allow it to work with different technologies and environments.

CPython: The standard and most widely used Python implementation, written primarily in C.

Jython: An implementation of Python that runs on the Java platform and integrates with Java.

IronPython: An implementation of Python that integrates with the .NET ecosystem and works with C# and other .NET languages.

These are different implementations of Python, rather than separate Python programming languages.

Platform Independence Python is considered a platform-independent language because the same Python source code can generally run on different operating systems, including Windows, macOS, and Linux, when the required Python version and dependencies are available.

For example, a Python program developed on Windows can usually run on Linux or macOS with little or no modification.

However, operating-system-specific features, external dependencies, and file paths may require changes.

High-Level and Low-Level Languages Programming languages can be classified according to how closely they communicate with the computer's hardware.

High-Level Languages
High-level languages are designed to be easier for humans to read, write, and understand. They hide many hardware-level details.

Examples include:

Python

JavaScript

Java

Low-Level Languages
Low-level languages are closer to the computer's hardware and machine instructions.

Examples include:

Machine language, which uses binary instructions.

Assembly language, which uses symbolic instructions that correspond closely to machine operations.

Low-level programming can provide greater control over hardware, but it is generally more difficult for humans to understand and write.

How Does a Computer Understand Input? Computers ultimately process information using binary representations, which consist of 0s and 1s.

Inputs can come in different forms, including text, audio, and images. These inputs are processed differently depending on the application.

Text: Encoded into numerical values using character-encoding systems such as UTF-8.

Audio: Represented as digital samples containing numerical values.

Images: Represented as numerical pixel values.

AI applications can process these numerical representations to recognize speech, analyze images, understand text, or generate responses.

However, not every input is simply converted into text first. The processing method depends on the type of input and the task.

History and Versions of Python Python was created by Guido van Rossum and first released in 1991.

Its major versions include:

Python 1.0 – 1994: The first major version, introducing core features of the language.

Python 2.0 – 2000: Introduced several improvements, including list comprehensions and garbage collection.

Python 3.0 – 2008: Introduced important language changes and improvements.

Python 3 is the modern version used for most new projects. Python 2 reached the end of its official support in January 2020.

Backward Compatibility
Backward compatibility means that newer versions of software can continue to support code written for older versions.

Python 3 introduced changes that made it incompatible with some Python 2 code. As a result, certain Python 2 programs require modifications before they can run on Python 3.

This is why developers should choose a supported Python version when starting a new project.

Programming Languages and Scripting Languages A programming language is a language used to write instructions that a computer can execute. A scripting language is commonly used to automate tasks, connect software components, and control the behavior of applications.

Compiled Languages
A compiler translates source code into another form, such as machine code or bytecode, before execution.

Examples include:

C++

Interpreted Execution
An interpreter executes program instructions at runtime, often without requiring the developer to create a separate native executable first.

Python and JavaScript are commonly described as interpreted or scripting languages, although their modern implementations may also use compilation and just-in-time techniques.

Python source code is commonly compiled into bytecode, which the Python virtual machine executes. Therefore, Python is not limited to purely line-by-line interpretation.

Python as a Scripting Language
Python is widely used for scripting because it has simple syntax and supports rapid development. It can automate tasks, process data, interact with databases, and manage files.

Python can also be used to develop large applications, backend systems, and complex software projects.

Disadvantages of Python Although Python has many advantages, it also has some limitations.

Performance: Python programs can be slower than compiled languages such as C or C++ for certain CPU-intensive tasks. Performance compared with Java depends on the workload and implementation.

Memory Consumption: Python objects and its runtime can use more memory than lower-level alternatives.

Runtime Errors: Some errors, including certain type-related errors, appear only when the affected code executes.

Mobile Development: Python is less commonly used for native mobile application development than languages and frameworks specifically designed for Android and iOS.

These limitations can often be managed through optimization, suitable libraries, testing, and choosing the right technology for the task.

Conclusion
Python is a versatile and beginner-friendly programming language that supports a wide range of applications, from basic scripting to advanced AI systems. Its readable syntax, extensive libraries, database connectivity, and cross-platform support make it a valuable tool for developers.

Learning Python provides a strong foundation for exploring data science, machine learning, artificial intelligence, web development, automation, and many other areas of technology.

Understanding useState, Rendering, and Targeting in React

Harish raj — Mon, 26 Oct 2026 17:28:28 +0000

Today, I learned how React works with useState, how to define logic using functions, how to render UI elements, and how to target a particular element to display updated data.

React makes it easier to build interactive user interfaces by updating the UI whenever the state changes.

Understanding useState in React useState is a React Hook used to store and manage data inside a functional component. When the state changes, React automatically re-renders the component.

Syntax:

const [value, setValue] = useState("");
value – stores the current state.

setValue – updates the state.

useState("") – initializes the state with an empty string.

Defining the Logic After creating the state, we define a function to perform an action. For example, when a user clicks a button, a function can update the state.

function greet() {
setMessage("Hello, Welcome to React!");
}
Here, the greet() function contains the logic, and setMessage() updates the state.

Rendering the UI In React, we use return() to render UI elements using JSX. JSX allows us to write HTML-like syntax inside JavaScript.

return (

Click Me

{message}

);
The button and heading are rendered on the page. When the button is clicked, the function updates the state, and React displays the new message.

Targeting an Element In React, we can display state data inside a specific JSX element using curly braces {}.

For example:

{message}

Here, the

element is the target where the message appears. When the state changes, React updates the displayed text automatically.

Complete Example import { useState } from "react";

function Greeting() {
const [message, setMessage] = useState("");

function greet() {
setMessage("Hello, Welcome to React!");
}

return (

Greet Me

{message}

);
}

export default Greeting;
How the Code Works
State: useState("") creates an empty message.

Logic: The greet() function updates the message.

Rendering: The return() statement displays the button and heading.

Targeting: The

element displays the updated message.

Re-rendering: React updates the UI after the state changes.

Conclusion
Today, I learned the basic workflow of React: creating state with useState, defining logic using functions, rendering elements using JSX, and displaying updated values in a target element.

Understanding these concepts is an important step toward building interactive React applications.

react js in paiyalagam

Harish raj — Sat, 24 Oct 2026 20:00:44 +0000

react is created by facebook . javascprit is library. prewitten code it is frame .before the react js if i click the second page it will take time and loading because different file for differnt page .so react solve this problem one html file for all the page. to create a react in terminal use npm create vite@content. oxlint and exlint .oxlint is stiict in warring and exlint is begginer friendly it will suggestion if make error to clear.render is used to run the appliaction .import and export.import is receive the jsx file in main.export is to sent he jsx file .SPA stands single page application is html .jsx is human and machine understand code user define tag.component header and footer is small for all page so it is fixed for all page so use component.

30/10/26 in payilagam

Harish raj — Wed, 30 Sep 2026 17:06:08 +0000

today i learn about how to create a object then what is objust .object is the state of compiantion and behaviour .const value are state .function is a behaviour. an objuct carrier function another function and variable.then learn about crud operation how to add new value in object then how to view then how to update the value and how to delete . this are all discussed today

29/09/2026 in payilagam

Harish raj — Tue, 29 Sep 2026 17:23:01 +0000

today learn about constructor .JavaScript Constructor Method A constructor in JavaScript is a special function used to create and initialize objects. It sets up object properties and is typically invoked using the new keyword. Constructors allow for the creation of multiple instances with similar properties and methods. Object.create() function in JavaScript
Object.create() in JavaScript is used to create a new object by setting an existing object as its prototype. Instead of copying properties directly or invoking a constructor, it establishes prototype-based inheritance, allowing the new object to access properties and methods from the specified prototype.

26/9/26 in payilagam

Harish raj — Sat, 26 Sep 2026 17:42:51 +0000

today i learn about js and function then what is parameter and arugment then how to use return end of the day sir give a project to create ecomerce site

23/9/2026 in payilagam

Harish raj — Wed, 23 Sep 2026 16:52:22 +0000

today last day of html css . i will done 6 project using html css . last project is clone the youtube page

today in payilagam

Harish raj — Wed, 23 Sep 2026 16:47:09 +0000

i will create a fb login page and instagram login page using html and css

day 5 in payilagam

Harish raj — Fri, 18 Sep 2026 17:44:52 +0000

today i will completed nav bar header in webpage .today i will learn media query and learn about position in css there are type static,absolute,relative,fixed and sticky.

day 4 in payilagam

Harish raj — Thu, 17 Sep 2026 17:25:02 +0000

today i learn about create header part in website using nav tag and using media queries then id and for input type .Font awesome is a website where they have n numbers icons.

day 3 in payilagam

Harish raj — Thu, 17 Sep 2026 17:10:48 +0000

today i learn how to create a resume using html and css . first i use grid box to separate box in column . then using img tag for profile photo .then learn about main asix and cross asis in flex then create a table for study details then push into gitlab